Organic Chemistry A2 Chapter 25-30 Debra Crawford.

Organic Chemistry A2 Chapter 25-30 Debra Crawford

Thank you for downloading and reviewing my slides
You are welcome to make changes Please repost the slides after you edits I would to see your edits IF you have any questions or would like help in find the answer key please me at Debra Crawford

Sources used in preparing this PowerPoint
Cambridge International AS and A Level Chemistry Coursebook Second Edition by Lawrie Ryan and Roger Norris ISBN: Cambridge International AS and A Level Chemistry Revision Guide by Judith potter and Peter Cann ISBN: Cambridge International AS and A Level Chemistry by Peter Cann and Peter Huges ISBN: Revision Guide Cambridge International AS and A Level Chemistry Second Edition by David Bevan ISBN: Organic Chemistry Second Edition by David Klein ISBN: Student Study Guide and Solution Manual for Organic Chemistry Second Edition by David Klein ISBN: Some yahoo search images

Meet 3 times a week for organic chemistry
Meet once a week for a double class of lab in preparation of paper 5 Debra Crawford

Year plan Review of organic Spend about 3 weeks on each chapter
Posters after chapter 28 Debra Crawford

Review organic chemistry from AS year

What is organic chemistry?
Studies of organic molecules and reactions Covalent compounds C Out number inorganic by 80:1 WHY? Debra Crawford

Types of formals Empirical formula Molecular formula
Structural formula Displayed formula Skeletal formula 3D displayed formula General formula Debra Crawford

Naming carbon chians Number of carbons in chain Name 1 2 3 4 5 6 7 8 9
10 Number of carbons in chain Name 1 Meth- 2 Eth- 3 Prop- 4 But- 5 Pent- 6 Hex- 7 Hept- 8 Oct- 9 Non- 10 Dec- Debra Crawford

Bonding Sigma Pi Hybridisation of C sp sp2 sp3 Debra Crawford

Functional groups Alkanes Alkenes Halogenoalkanes Alcohols Aldehydes
Ketones Carboxylic acids Esters Review General formula What the fuctional group looks look How to name Debra Crawford

Isomers Greek words isos and meros, meaning “made of the same parts.”

Debra Crawford

Organic reaction -mechanisms
Homolytic fission Heterolytic fission Debra Crawford

Homolytic fission When a covalent bond breaks by splitting the shared pair of electrons between the two products Produces two free radicals, each with an unpaired electron Debra Crawford

Free radical What is an r group Debra Crawford

Debra Crawford

Initiation step Propagation step Termination step Debra Crawford

Debra Crawford

Heterolytic fission When a covalent bond breaks with both the shared electrons going to one of the products Produces two oppositely charged ions Debra Crawford

Carbocation Positive induction effect Debra Crawford

Electrophile Electron-deficient species which is therefore attracted to parts of molecules which are electron rich Positive ions or have a partial positive charge Debra Crawford

Nucleophile Electron-rich species which is therefore attracted to parts of molecules which are electron deficient Nucleophile have lone pair of electrons and may also have a negative charge Debra Crawford

Types of organic reactions
Addition Elimination Substitution Hydrolysis Oxidation Reduction Debra Crawford

Addition Debra Crawford

Elimination and Substitution
This chapter introduces a class of reactions, called substitution reactions, in which one group is exchanged for another, while Chapter 8 introduces elimination reactions, characterized by the formation of a p bond: Debra Crawford

Hydrolysis Debra Crawford

Oxidation and Reduction
Debra Crawford

Debra Crawford

Benzene and its compounds
Chapter 25 Benzene and its compounds

The benzene ring Debra Crawford

Benzene was first isolated and identified in 1825 by Michael Faraday
Debra Crawford

Debra Crawford

It is important to understand the meaning of the double-headed arrow,
It is important to understand the meaning of the double-headed arrow, . This states that there is only one structure, which is in between the two ‘classical’ structures drawn either side of the arrow. The existence of a structure which cannot be represented by a single ‘classical’ structure, but which is intermediate between several of them, is known as mesomerism (from the Latin/Greek work meso, meaning ‘middle’). The classical structures are called mesomers. Debra Crawford

Debra Crawford

All the bond angles in benzene are 120°
All the bond angles in benzene are 120°. All the C¬C bonds have the same length, 0.139 nm. This is intermediate between the length of the C ¬C bond in an alkane (0.154 nm) and the C“C double bond in an alkene (0.134 nm). Debra Crawford

Debra Crawford

Joining of benzene Two ways Debra Crawford

Naming Isomerism Two ways to name position 1,2,3,4,5,
Or ortho-, meta- and para- Go to the first try now problem and name Debra Crawford

Debra Crawford

Monosubstitution Bromobenzene Nitrobenzene Ethylbenzene Propylbenzen
Phenol Debra Crawford

Draw out all possible positional isomers of C6H3Br2OH and name them.
Debra Crawford

When the benzene ring is the substituent Phenyl
Debra Crawford

Reactions of arenes Electrophilic substitution with Cl/Br
Nitration of benzene Alkylation of benzene Debra Crawford

Combustion Complete Incomplete Debra Crawford

klein Debra Crawford

Electrophilic substitution with Cl/Br
Alkene Electrophilic addition Debra Crawford

Electrophilic substitution
Arenes Electrophilic substitution Debra Crawford

Step 1 catalyst Warming Anhydrous AlCl3 or AlBr3 or FeBr3
Debra Crawford

Debra Crawford

Same reason but only AlCl3 as catalysit
Debra Crawford

Klein Debra Crawford

Debra Crawford

Have students come up with the mechanism
Debra Crawford

Boiling not catalast mechanicam Debra Crawford

Nitration Warm 55˚C Debra Crawford

Debra Crawford

Further sub on 3,5 Debra Crawford

Debra Crawford

Friedel-Crafts reaction
Electrophilic substitution Debra Crawford

Friedel-Crafts Alkylation
Debra Crawford

Debra Crawford

sp3 hybridized NO2 incompatibile Debra Crawford

Debra Crawford

Frieldel-Crafts Acylation
Debra Crawford

Debra Crawford

Oxidation of side chain
Whole side chain Debra Crawford

Debra Crawford

Hydrogenation Debra Crawford

Phenol C6H5OH Melting point 43˚C Crystalline solid Debra Crawford

Phenol naming Phenol Hydroxy substituent Halogen Nitro Amino Alkyl
Aldehyde Ketone Carboxylic acid Debra Crawford

a 3,5-dichlorophenol b 2-hydroxy-4-methylbenzoic acid
2,6-diethylphenol Debra Crawford

Debra Crawford

Acidity Weak acid Debra Crawford

Higher the number weaker the acid
Debra Crawford

Resonance Induction Solvation effects Debra Crawford

Resonance As a result, phenol does not need to
be deprotonated with a very strong base like sodium hydride. Instead, it can be deprotonated by hydroxide. Debra Crawford

Induction Trichloroethanol is four orders of magnitude (10,000 times) more acidic than ethanol, because the conjugate base of trichloroethanol is stabilized by the electron-withdrawing effects of the nearby chlorine atoms. Debra Crawford

Solvation effect The pKa values indicate that tert-butanol is less acidic than ethanol, by two orders of magnitude. This difference in acidity is best explained by a steric effect. The ethoxide ion is not sterically hindered and is therefore easily solvated (stabilized) by the solvent, while tert-butoxide is sterically hindered and is less easily solvated (Figure 13.4). The conjugate base of tert-butanol is less stabilized than the conjugate base of ethanol, rendering tert-butanol less acidic. Debra Crawford

Debra Crawford

Reactions of phenol Reaction of –OH group Breaking O-H bond
Substitution of OH in benzene ring First none due to strong C-O bond Debra Crawford

O-H bond Dissolves in alkaline solutions Sodium Bases
Bases on alcohol reaction Debra Crawford

Esterification Debra Crawford

Substitution reaction
More susceptible to electrophilic attack Debra Crawford

No catalyst needed Debra Crawford

Coupling Debra Crawford

Test for phenols Br2 Debra Crawford

Preparing phenols Debra Crawford

Uses of phenols Antiseptics/disinfectants
1867 dilute solution of phenol in water Problem to too corrosive to be of general use as an antiseptic. Debra Crawford

Uses of phenols Analgesics painkilling and fever-reducing
Willow bark (16th century) salicylic acid 1893 The therapeutic use of salicylic acid was limited, however, because it caused vomiting and bleeding of the stomach. In 1893 an ester derived from salicylic acid and ethanoic acid was found to have far fewer side-effects Aspirin is the most widely used of all analgesics. However, it still retains some of the stomach-irritating effects of salicylic acid. A less problematic painkiller is paracetamol, which is another phenol Debra Crawford

Carboxylic Acids and Their Derivatives
Chapter 26 Carboxylic Acids and Their Derivatives

The acidity of carboxylic acids
H+ reactes with bases to make salts Carboxylates Sodium ethanoate CH3COO-Na+ Weak acid Most are undissociated in water Smaller Ka weaker acid Larger pKa weaker acid Debra Crawford

Relative acidities from demonstration
Na, NaOH and Na2CO3 are weaker bases and need stonger acids to react Debra Crawford

Electron-withdrawing groups bonded to the carbon atom next to the COOH group make the acid stronger. There are two reasons for this: ■■ electron-withdrawing groups further weaken the O H bond in the undissociated acid molecule ■■ electron-withdrawing groups extend the delocalisation of the negative charge on the COO– group of the carboxylate ion, further increasing the stabilising of the COO– group and making it less likely to bond with an H+(aq) ion. Ethanoic acid is the weakest acid in Table 26.1, as the methyl group is electron donating. This has the opposite effect to electron-withdrawing groups: ■■ it strengthens the O H bond in the acid’s COOH group ■■ it donates negative charge towards the COO– group of the carboxylate ion, making it more likely to accept an H+(aq) ion. Debra Crawford

Debra Crawford

a The lower the pKa, the larger is Ka
a The lower the pKa, the larger is Ka. This means that the acid is more dissociated, and therefore stronger. Hence fl uoroethanoic acid is a stronger acid than chloroethanoic acid. This is due to the greater electron-withdrawing ability of the highly electronegative fluorine atom. b Difl uoroethanoic acid would be expected to have a lower pKa than dichloroethanoic acid – about 1.0. Debra Crawford

One CH3 group raised pKa by about. 1unit so three with raise it about
One CH3 group raised pKa by about .1unit so three with raise it about .3 unit from ethanoic acid. Actual value 5.03 Electron withdrawing effects of the Cl atom will be reduced by the extra CH2 group so pKa with be more than 4.76 but less than Actual Value 3.98 As Cl atom is further away from the –CO2H group the effect reduces. Between other two. Actual value 4.05 Debra Crawford

Acidity and benzene Debra Crawford

Oxidation of two carboxylic acids
Methanoic acid Ethanedionic acid Have students draw both Debra Crawford

HCOOH acidified dichromate(VI) Potassium manganite(VII)
Fehling’s solution and Tollens’ reagent Dichromate oragane to green K decolorizing purple Debra Crawford

HOOCCOOH Potassium manganite(VII) Debra Crawford

Acyl chlorides -OH group of carboxylic acid is replaced with Cl
Debra Crawford

How to make Second one needs heat Debra Crawford

Debra Crawford

RSC Stater for 10 Carbonyl chemistry 4.3
Answers in class Debra Crawford

Why do we want arcy chlorides
Carboxylic acid are quite unreactive Arcy chlorides are more reactive than carboxylic acid This effect renders the carbonyl group even more electrophilic when compared with the carbonyl group of a ketone. Review electrophilic with students acceptor of a pair of electrons Debra Crawford

In second the the C-N bond is hard to break
C-N bond is a lot like double bond Debra Crawford

Debra Crawford

Intermolecular forces
Van der waals Dipole dipole Debra Crawford

Debra Crawford

Please explain the effects of the carboxyl group.
effect of increasing the boiling point by about 10–15 °C compared with the boiling point of the halogenoalkane with similar shape Debra Crawford

Reactions Water Alcohols Phenols Ammonia Amines Debra Crawford

Water Hydrolysis Debra Crawford

Aryl chlorides, such as chlorobenzene, will not undergo hydrolysis
Debra Crawford

Alcohols Pyridine Neutralize acid Debra Crawford

Phenols phenols are not so nucleophilic as alcohols, because the
lone pair on the oxygen atom is delocalised over the ring. The acylation of phenols is therefore usually carried out under basic conditions Debra Crawford

Ammonia Therefore an excess of amine or ammonia is used to ensure complete reaction. The reactions of amides are described in section 27.5. Debra Crawford

Amines Have students make mechainm
There are three steps: (1) nucleophilic attack, (2) loss of a leaving group to re-form the carbonyl, and (3) proton transfer to remove the positive charge Debra Crawford

Debra Crawford

21:50 Organic Chemistry Klein Student study guide and solutions Klein Debra Crawford

Debra Crawford

Reduction 1 As we saw in the panel on page 445, the unsaturated nature of the C“ O bond allows the C¬OH bond to be formed before the C¬Cl bond has broken. This addition-elimination mechanism therefore has a lower activation energy than the straight SN2 reaction. 2 The carbon atom in acyl chlorides is attached to two electronegative atoms (oxygen and chlorine), and so is polarised + to a greater extent than the carbon atom in chloroalkanes. This allows it to attract nucleophiles more strongly. Debra Crawford

This reducing agent will react with the acid chloride rapidly but will react with the aldehyde more slowly, allowing the aldehyde to be isolated. These conditions can be used to convert an acid chloride into an aldehyde. Debra Crawford

Debra Crawford

Predict the major product(s) for each of the following reactions:
21:18 Organic Chemistry Klein Debra Crawford

Organic Chemistry Klein
Student study guide and solutions Klein Debra Crawford

Organic Nitrogen Compounds
Chapter 27 Organic Nitrogen Compounds

Amines Three classes Primary Secondary Tertiary Debra Crawford

Naming Amines Primary amine When not the main group amino-
All besides halogens Debra Crawford

Secondary and Tertiary Name each group
If amine is not main group use N- is show that it is on the N 2,2-Dichloro-N-ethyl-N-methyl-3-hexanamine Debra Crawford

Naming Debra Crawford

Draw and name Cyclohexylmethylamine Tricyclobutylamine
2,4-Diethylphenylamine 2-Methylcyclohexanamine ortho-Aminobenzaldehyde Debra Crawford

What is the hybridizion on N in an amine
Pyramidal inversion of an amine enables the enantiomers to rapidly interconvert at room temperature. Debra Crawford

Debra Crawford

Intermolecular forces
Debra Crawford

Debra Crawford

Basicity of amines Base is a H+ proton acceptor
N donates its lone pair to the H+ forming a co-ordinate bond Debra Crawford

One of the most important properties of amines is their basicity
One of the most important properties of amines is their basicity. Amines are generally stronger bases than alcohols or ethers, and they can be effectively protonated even by weak acids. In this example, triethylamine is protonated using acetic acid. Compare the pKa values of acetic acid (4.76) and the ammonium ion (10.76). Recall that the equilibrium will favor the weaker acid. In this case, the ammonium ion is six orders of magnitude weaker than acetic acid, and therefore, the amine will exist almost completely in protonated form (one in every million molecules will be in the neutral form). This example illustrates how the basicity of an amine can be quantified by measuring the pKa of the corresponding ammonium ion. A high pKa indicates that the amine is strongly basic, while a low pKa indicates that the amine is only weakly basic. Table 23.1 shows pKa values for the ammonium ions of many amines. Debra Crawford

Delocalization Effects
Debra Crawford

Debra Crawford

Formation of amines NH3 CN- Reduction Debra Crawford

Nucleophilic substitution
Hot ethanolic ammonia Pressure Debra Crawford

Debra Crawford

Excess ammonia must be used
Debra Crawford

Debra Crawford

Replace halogen Cyano group Nitrile Go over how to make carboycil acid
Debra Crawford

Nucleophilic substitution
Heated under reflux Sodium cyanide Potassium cyanide In ethanol Debra Crawford

Debra Crawford

Bromine water It causes the lone pair to be much less basic (see above) and also much less nucleophilic. ● It causes the ring to be more electron rich, and so to undergo electrophilic substitution reactions much more readily than benzene. The enhanced reactivity of phenylamine in this regard is similar to that of phenol (see Topic 25, page 434), an example being the ease with which phenylamine decolorises bromine water Only the shorter-chained amines (with fi ve or fewer carbon atoms) are soluble in water, but the ionic nature of their salts allows all amines to dissolve in dilute aqueous acids. Debra Crawford

Reactions as nucleophiles
alkyl and acyl halides Debra Crawford

alkylated to quaternary ammonium salts
excess of a bromoalkane, amines can be successively alkylated, first to secondary and then to tertiary amines alkylated to quaternary ammonium salts Quarternary ammonium salts are water-soluble solids, with no basic character at all, because there is no lone pair of electrons on the nitrogen atom. An important naturally occurring ammonium salt is choline. Phosphatidylcholine is a key phospholipid component of cell membranes. Acetylcholine is an important neurotransmitter, allowing a nerve impulse to pass from the end of one nerve to the start of the next one Debra Crawford

Reaction with nitrous acid (nitric(III) acid)
Nitrous acid, HNO2, is unstable Aryl amines, however, form fairly stable diazonium salts at low temperatures Debra Crawford

Diazotisation Aryl amines, however, form fairly stable diazonium salts at low temperatures Not stable above 10C Debra Crawford

Coupling Debra Crawford

Debra Crawford

Amino acids Amino group -NH2 Carboxylic group –COOH
2-amino-carboxylic acid RCH(NH2)COOH Debra Crawford

White solids High melting points Solubility Debra Crawford

Zwitterion Amphoteric Resist change in pH Chiral center Carbon
Debra Crawford

For each amino acid, there is a specific pH at which the concentration of the zwitterionic form reaches its maximum value. This pH is called the isoelectric point (pI), and each amino acid has its own unique pI. For amino acids that lack an acidic or basic side chain, the pI is simply the average of the two pKa values. The following example shows the calculation for the pI of alanine. Debra Crawford

Reactions of amino acids
Acylated Nitrous acid Esterifed Buffers Reactions for R groups Debra Crawford

Debra Crawford

Use date booklet Debra Crawford

Peptides Condensation reaction Amino Acids 2- dipeptide 3 – tripeptide
Polypeptide Protein Debra Crawford

ORDER MATTERS Debra Crawford

Debra Crawford

Peptide chains always have an amino group on one end, called the N terminus, and a COOH group on the other end, called the C terminus (Figure 25.4). By convention, peptides are always drawn with the N terminus on the left side. Debra Crawford

How many possible tripeptides can be formed from the three amino acids Gly, Ala and Ser, if each tripeptide contains all three amino acids? six Debra Crawford

Debra Crawford

Amides R and R can be alkyl, aryl or hydrogen
Extensively hydrogen bonded Hδ+ atoms (on nitrogen) Lone pairs on N and O Unlike amines, amides form neutral solutions in water, and can be protonated only by strong acids So, although amides are more basic (through their oxygen atom) than other carbonyl compounds (because of the electron donation from nitrogen), they are still much less basic than conventional nitrogen bases such as amines. Debra Crawford

Debra Crawford

Reactions of the amides
Preparation Hydrolysis Reduction Debra Crawford

Preparation Need excess of amine Debra Crawford

Hydrolysis Because of the high degree of positive charge on the carbon atom in protonated amides, they are susceptible to nucleophilic attack. Hydrolysis is usually carried out in dilute sulfuric acid. It is still quite a slow Amides can also be hydrolysed under basic conditions, by heating with NaOH(aq). Debra Crawford

Debra Crawford

Reduction Debra Crawford

Debra Crawford

Electrophoresis Biochemical analysis
Separate, identity and purify proteins Paper Gel Debra Crawford

Debra Crawford

http://www. columbia. edu/cu/biology/courses/c2005/images/paperelec
Debra Crawford

Debra Crawford

Isoelectric point (pI) Amino acids have zwitterionic forms
pH where that form is most likely The greater the different between the buffer and pI the further the amino acid will travel in paper electhoresis Back to paper and amino acids Debra Crawford

Finding pI For amino acids with acidic or basic side chains, the pI is the average of the two pKa values that correspond with the similar groups. For example, the pI of lysine is determined by the two amino groups, while the pI of glutamic acid is determined by the two carboxylic acid groups. Debra Crawford

Handed out a copy of table 25.2 each student

Klein page 1198 Debra Crawford

Chapter 28 Polymerisation

Addition polymerisation
Debra Crawford

Debra Crawford

Condensation polymerisation
Type I Type II Debra Crawford

Debra Crawford

Synthetic polyamides Polyamide Peptide link -NH2 -COOH -COCl
What is a peptide link Ring-opening polymerisation Debra Crawford

Kevlar Debra Crawford

Debra Crawford

Biochemical polymers Protein 16% of the human body
Condensation polymerization Unbranched Unique sequence of amino acids Sequence determined by DNA Particular biological function What type of polymer are protein Debra Crawford

Protein Structure Primary Secondary Tertiary
Review three terms in terms of alcohol Debra Crawford

Primary Order of amino acids Numbered from N-terminal Covalent bonding
Debra Crawford

Debra Crawford

Secondary Three‑dimensional conformations of regions of the protein
Debra Crawford

a-helix a helix forms when a portion of the protein twists into a clockwise spiral Each turn has approximately four amino acid residues, Each C=O group experiences hydrogen bonding with an N-H group that is four residues farther along on the chain. Illustration, Irving Geis. Image from Irving Geis Collection/Howard Hughes Medical Institute Debra Crawford

Illustration, Irving Geis
Illustration, Irving Geis. Image from Irving Geis Collection/Howard Hughes Medical Institute Debra Crawford

Β-pleated sheet Hydrogen bonding occurs between the C=O group and N-H group of neighboring strands R groups (side chains) are positioned above and below the plane of the sheet, in an alternating pattern Illustration, Irving Geis. Image from Irving Geis Collection/Howard Hughes Medical Institute Debra Crawford

Illustration, Irving Geis
Illustration, Irving Geis. Image from Irving Geis Collection/Howard Hughes Medical Institute Debra Crawford

Debra Crawford

Alpha helices in the two peptide chains of human insulin
Debra Crawford

Tertiary Further folding of polypeptide chain Disulfide bridges
Weak van der Waals’ forces Relatively weak hydrogen bonds Ionic bonds (salt bridges) Have students with book shut explain four terms Debra Crawford

Disulfide bridges Usually found in proteins that outside the body cells Debra Crawford

Weak van der Waals’ forces
Non-polar Total can be considerable A large proportion of amino acids Debra Crawford

Relatively weak hydrogen bonds
Debra Crawford

Ionic bonds (salt bridges)
Between side chains Debra Crawford

Debra Crawford

Hydrolysis of proteins
HCl Cl–H3N+ RCH COOH acid reflux NaOH H2N RCH COO–Na+ excess of alkali, refllux Debra Crawford

The importance of hydrogen bonding in DNA
Deoxyribonucleic acid Can copy itself Stores information for making proteins Monomers Nucleoside phosphates Debra Crawford

Nucleoside phosphates
Sugar Deoxyribose 5 membered ring Phosphate group Nitrogen-containing base Four types Debra Crawford

Have students build with modeling kits and self determine shape and bonding between bases
Debra Crawford

Debra Crawford

` Debra Crawford

Debra Crawford

Complementary base pairs
A always pairs with T forming two hydrogen bonds between them G always pairs with C forming three hydrogen bonds between them the two strands are twisted to form a double helix ■■ the nitrogen-containing bases link the two strands ■■ the bases are positioned at right angles to the long axis of the helix (rather like a pile of coins) ■■ the bases are linked by hydrogen bonds. Debra Crawford

Debra Crawford

DNA replication The hydrogen bonds and van der Waals’ forces between the base pairs in part of a DNA molecule are broken. This part of the double helix unwinds. Nucleotide triphosphates are brought up one by one to the separated part of the chain. Enzymes catalyse the polymerisation reaction.. Debra Crawford

Debra Crawford

Polyesters Dicarboxylic acids Diols Acid hydrolysis of polyesters
Debra Crawford

Terylene® benzene-1,4-dicarboxylic acid ethane-1,2-diol
antimony(III) oxide 280 °C Debra Crawford

Poly(lactic acid) PLA lactic acid 2-hydroxypropanoic acid
raw material is starch from corn biodegradable Debra Crawford

Designing useful polymers
Density Low-density High density Stronger and higher melting points Debra Crawford

Non-solvent-based adhesives
Traditional adhesives Flammable Pollution Silicon bonded to oxygen -Si-O-Si- Debra Crawford

Reaction is initiated by presence of moisture
Thermosets Very strong Cannot be melted Cannot be remolded Reaction is initiated by presence of moisture Debra Crawford

Degradable polymers What are problems with plastics? Biodegradable
Photodegradable Debra Crawford

Biodegradable Decomposed By microorganisms Debra Crawford

Photodegradable C=O Ultraviolet Debra Crawford

Conducting polymers Conduct electricity Conjugated double bonds
One dimensional delocalized electrons Doping Adding other substances to increase conductivity Debra Crawford

Debra Crawford

Advantages over metals
Not corrode Less dense Can be shaped easier Disadvantages to metals Less conductive Uses Led Solar panals Debra Crawford

Polymer deductions Predict the type of polymerisation reaction for a given monomer or pair of monomers Deduce the repeat unit of a polymer obtained from a given monomer or pair of monomers Deduce the type of polymerisation reaction that produces a given section of a polymer molecule Identify the monomer(s) present in a given section of a polymer molecule. Debra Crawford

Addition polymers C=C Condensation Linking Ester Amide Debra Crawford

Organic Chemistry Review
Review Chapters 24-28 Organic Chemistry Review

What are mechanism Shows the movement of electrons Changes in bonds
What do the arrows mean? Debra Crawford

Debra Crawford

Preparation of Nitriles
Debra Crawford

Preparation of Nitriles from Amides
Debra Crawford

Debra Crawford

Chapter 29 Analytical Chemistry

Chromatography Paper chromatography Two-way chromatography
Thin-layer chromatography High-performance liquid chromatography Gas-liquid chromatography Separating a mixture in to pure compounds Debra Crawford

History of Chromatography
Invented by Mikhail Tsvet Russian scientist Early 20th century (1900’s) Coloured plant pigments Today most chromatography is carried out on colourless compounds Debra Crawford

Paper chromatography Think back to IG Mobile phase Stationary phase
Rf value Have students design a lab for paper chromatography and do lab following their directions Debra Crawford

A paper chromatogram of an amino acid mixture with five ‘references’ spotted alongside, before and after development with ninhydrin Debra Crawford

Two-way chromatography
Debra Crawford

Although it may appear dry to the touch, chromatography paper (which is like smooth filter paper but with an accurate and constant thickness) contains water molecules hydrogen-bonded to the OH groups on its cellulose molecules. This layer of water molecules is the stationary phase. The moving phase is chosen to be less polar than water. It is usually an organic solvent, or a mixture of solvents: ethanol or an ethanol–water mixture is often used. Debra Crawford

Thin-layer chromatography
Technique is similar to paper chromatography Theory is different Debra Crawford

TLC relies on the fact that the attractive forces that cause different compounds to be adsorbed onto a solid surface differ from one compound to another How readily this occurs depends on both how soluble a particular compound is in the solvent, and how strong the attraction is between the compound and the solid support Debra Crawford

High-performance liquid chromatography
It relies on pumps to pass a pressurized liquid solvent containing the sample mixture through a column filled with a solid adsorbent material. Each component in the sample interacts slightly differently with the adsorbent material, causing different flow rates for the different components and leading to the separation of the components as they flow out the column. Debra Crawford

Play video Debra Crawford

Output High Performance Liquid Chromatography
The output will be recorded as a series of peaks - each one representing a compound in the mixture passing through the detector and absorbing UV light The area under the peak is proportional to the amount of X which has passed the detector, and this area can be calculated automatically by the computer linked to the display. The area it would measure is shown in green in the (very simplified) diagram. Debra Crawford

Gas chromatography Debra Crawford

Length and diameter of column Chemical make up of the solvent
In order to compare Flow rate Temperature Length and diameter of column Chemical make up of the solvent Polarity of the stationary phase Debra Crawford

Retention time Measurement of the time it takes a substance to reach the defector / travel through the stationary phase Debra Crawford

Which peaks are good? Debra Crawford

Debra Crawford

http://blog. restek. com/wp-content/uploads/2012/08/OCPs-H2-CSR-LVSI
Debra Crawford

https://www. vernier. com/images/magnify/gc-mini_Quantifying-a-mixture
Debra Crawford

Proton (1H) nuclear magnetic resonance
NMR Nuclear magnetic resonance Each H atom behaves like a tiny magnet Line up with or spin against magnetic field Debra Crawford

Debra Crawford

Mixes well with most organic compounds Only one peak
Tetramethylsilane TMS Si(CH3)4 Inert Volatile liquid Mixes well with most organic compounds Only one peak Debra Crawford

Chemical shift δ Measured in ppm (parts per million)
Shift away form the TMS line Debra Crawford

Low-resolution NMR Single peak for each non-equivalent hydrogen atom
Zero point on the x-axis is on the right Area under the peak tells use the relative number of equivalent H atoms Shown with labels 1H, 2H, 3H Debra Crawford

Debra Crawford

High resolution NMR Peaks that appear as a single peak on low resolution are often a group of close peaks Splitting pattern Caused by interference is called spin–spin coupling Depends on the number of hydrogen atoms on the adjacent carbon atom or atoms n + 1 rule Debra Crawford

Debra Crawford

Equivalent protons don’t split
Splitting is most commonly observed when protons are separated by either two or three σ bonds; Debra Crawford

Debra Crawford

16. 17 Below are NMR spectra of several compounds
16.17 Below are NMR spectra of several compounds. Identify whether these compounds are likely to contain ethyl, isopropyl, and/or tert-butyl groups: Debra Crawford

-OH and –NH- signal Field strength at which they resonate depends on the acidity and hydrogen-bonding ability Easy proton exchange with other O—H or N—H protons in the sample, These protons often do not cause the splitting of the peaks of adjacent proton of the solution Debra Crawford

Deuterium exchange Heavy water D2O (D = 2H)
Peaks due to the —OH or —NH2 protons disappear Deuterium atoms do not absorb in the same region of the electromagnetic spectrum as protons Debra Crawford

Debra Crawford

Analyzing a 1H NMR Spectrum
Always begin by inspecting the molecular formula Consider the number of signals and integration of each signal Analyze each signal Assemble the fragments into a molecular structure Debra Crawford

Debra Crawford

Carbon-13 NMR spectroscopy
Simpler than a 1H spectrum Absorbances in a 13C spectrum usually appear as singlets Very small natural abundance of 13C atoms (1.1%), the chances of two adjacent carbon atoms in a molecule both being 13C atoms is only just over 1 in 100, and so the splitting of a peak due to adjacent 13C atoms is very unlikely Debra Crawford

Solvent CDCl3 Small peak at 80ppm Debra Crawford

Debra Crawford

Predicting the number of signals and approximate location of each signal in a 13C NMR spectrum
Debra Crawford

Debra Crawford

Putting it together Debra Crawford

DEPT 13C NMR Spectroscopy
a broadband-decoupled 13C spectrum does not provide information regarding the number of protons attached to each carbon atom in a compound DEPT 13C NMR spectroscopy utilizes two rf transmitters and relies on the fact that the intensity of each particular signal will respond to different pulse sequences in a predictable fashion, depending on the number of protons attached Debra Crawford

Mass spectrometry Mass spectrometry
study of the interaction between matter and an energy source other than electromagnetic radiation. Used primarily to determine the molecular weight and molecular formula of a compound. Review the how used to find isotope mass and relative atomic mass Debra Crawford

Compound is first vaporized and converted into ions
Which are then separated and detected. The most common ionization technique involves bombarding the compound with high-energy electrons. These electrons carry an extraordinary amount of energy, usually around 1600 kcal/mol, or 70 electron volts (eV). When a high-energy electron strikes the molecule, it causes one of the electrons in the molecule to be ejected. This technique, called electron impact ionization (EI), generates a high-energy intermediate that is both a radical and a cation. Debra Crawford

This radical cation, symbolized by (M)+•, is called the molecular ion, or the parent ion.
The molecular ion is often very unstable and is susceptible to fragmentation, which generates two distinct fragments. Debra Crawford

Only ions are measure as only they are deflected
Debra Crawford

tallest peak in the spectrum is assigned a relative value of 100%
Cations are separated by their mass-to-charge ratio (m/z). The charge (z) on most ions is +1, and therefore, m/z is effectively a measure of the mass (m) of each cation plot is then generated mass spectrum tallest peak in the spectrum is assigned a relative value of 100% Base peak Debra Crawford

Debra Crawford

peak m/z = 17. This peak, called the (M+1)+• peak
Debra Crawford

Analyzing the (M)+• Peak
Some compounds, the (M)+• is the base peak Most compounds will easily fragment, and the (M)+• peak will not be the most abundant ion In some cases, it is possible for the (M)+• peak to be entirely absent, if it is particularly susceptible to fragmentation Debra Crawford

Debra Crawford

Can be used to distinguish compounds
When analyzing a mass spectrum, the first step is to look for the (M)+• peak, because it indicates the molecular weight of the molecule Can be used to distinguish compounds Debra Crawford

Useful information can also be obtained by analyzing whether the molecular weight of the parent ion is odd or even Odd molecular weight generally indicates an odd number of nitrogen atoms in the compound Even molecular weight indicates either the absence of nitrogen or an even number of nitrogen atoms nitrogen rule Debra Crawford

Debra Crawford

High-resolution mass spectra
can distinguish between ions that appear to have the same mass on a low resolution mass spectrum molecular ion peak at 45 could be caused by C2H7N or CH3NO C2H7N+ peak at CH3NO+ peak at Debra Crawford

Debra Crawford

Using the [M + 1] peak Two stable isotopes of carbon, 12C and 13C
Relative abundances are 98.9% for 12C and 1.1% for 13C Number of carbon atoms Debra Crawford

Debra Crawford

How many carbons in each
Debra Crawford

Debra Crawford

M+2 and M+4 peaks Cl Br Debra Crawford

Debra Crawford

15. 24 Below are mass spectra for four different compounds
15.24 Below are mass spectra for four different compounds. Identify whether each of these compounds contains a bromine atom, a chlorine atom, or neither. Debra Crawford

Simple fragmentation Debra Crawford

Debra Crawford

Do second one on black broad with students
Debra Crawford

Debra Crawford

Applications of the mass spectrometer
Can be link to gas-liquid chromatography Compared to known compounds In research used to confirm structure of undiscovered molecules Debra Crawford

Chapter 30 Organic Synthesis

Designing new medicinal drugs
Predict the shape Functional groups Molecule modelling Identifying macromolecules Debra Crawford

Chirality in pharmaceutical synthesis
Enantiomers Optically active Racemic mixtures Debra Crawford

Prue enantiomers Lower dosage Minimizes rick of side effects
Optical resolution Using optically active starting points Using a chiral catalyst Debra Crawford

Synthetic routes Work backwards
Starting with commonly available raw materials Adding C atoms Debra Crawford

Goals Predicting the reactions of complex molecules you have never seen before, containing more than one functional group Suggesting a series of reaction to make a given compound from a given staring point Debra Crawford

Review all organic chemistry

R = hydrogen or methyl or other alkyl unless stated otherwise
Debra Crawford R = hydrogen or methyl or other alkyl unless stated otherwise

Debra Crawford

Debra Crawford R = hydrogen or methyl or other alkyl unless stated otherwise

Debra Crawford

Aldehydes Ketones Carboxylic acids Phenols Esters Acyl chlorides
Amides Amines Triiodomethane Debra Crawford

Pg 531 Debra Crawford

Chapter P2 Practical Skills two

Written examination of practical skills
Paper 5 Not in the LAB Two question 30 points Planning Analysis, conclusions, and evaluations Debra Crawford

Test percentage to A-level grade
40 points 30 points 60 points 100 points 40 points Debra Crawford

Planning Two parts Defining the problem Methods Debra Crawford

Defining the problem Make a hypothesis/prediction
Identify independent and dependent variables Debra Crawford

Methods How to do experiment
Can’t ask you for help if directions are unclear Need to understand basic techniques and why used Draw apparatus and understand how to use data in relevant calculations Debra Crawford

How to lay out data Safety precautions Accuracy of data Fume hood
Gloves Accuracy of data Debra Crawford

Analysis ~Dealing with Data
Read table of data Use data to find patterns and anomalous Averages Graphs Scales for axis To include (0,0) Debra Crawford

Evaluations Identify anomalous Quality of results and apparatus
Appropriate Accurate Percent error Debra Crawford

Conclusions Compare to hypothesis Graph Improvements Debra Crawford

Organic Chemistry A2 Chapter 25-30 Debra Crawford.

Similar presentations

Presentation on theme: "Organic Chemistry A2 Chapter 25-30 Debra Crawford."— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Organic Chemistry A2 Chapter 25-30 Debra Crawford.

Similar presentations

Presentation on theme: "Organic Chemistry A2 Chapter 25-30 Debra Crawford."— Presentation transcript:

Similar presentations

About project

Feedback