Organic Chemistry.

Organic Chemistry

Outline Introduction Special nature of carbon
Classification of Organic Chemistry Homologous Series & General Characteristics Separation of Petroleum & Cracking Types of formula Isomerism I.U.P.A.C Nomenclature Compounds of different functional groups

Introduction Organic chemistry is the study of carbon compounds. There are around 6 millions compounds of C already known. Not all C-compounds are organic CO, CO2 considered inorganic Organic compounds  covalently bonded compounds containing carbon, excluding carbonates and oxides

Special nature of carbon
Carbon can join with other carbon atoms to form Long chain carbon atoms Branch chain carbon atoms Rings of carbons Multiple bonds between carbon atoms and atoms of other elements Why is it possible for carbon to do so?

SPECIAL NATURE OF CARBON - CATENATION
CATENATION is the ability to form bonds between atoms of the same element. Carbon forms chains and rings, with single, double and triple covalent bonds, because it is able to FORM STRONG COVALENT BONDS WITH OTHER CARBON ATOMS Carbon forms a vast number of carbon compounds because of the strength of the C-C covalent bond. Other Group IV elements can do it but their chemistry is limited due to the weaker bond strength. BOND ATOMIC RADIUS BOND ENTHALPY C-C nm kJmol-1 Si-Si nm kJmol-1 The larger the atoms, the weaker the bond. Shielding due to filled inner orbitals and greater distance from the nucleus means that the shared electron pair is held less strongly.

CHAINS AND RINGS THE SPECIAL NATURE OF CARBON
CARBON ATOMS CAN BE ARRANGED IN STRAIGHT CHAINS BRANCHED CHAINS and RINGS You can also get a combination of rings and chains

THE SPECIAL NATURE OF CARBON MULTIPLE BONDING AND SUBSTITUENTS
CARBON-CARBON COVALENT BONDS CAN BE SINGLE, DOUBLE OR TRIPLE

THE SPECIAL NATURE OF CARBON MULTIPLE BONDING AND SUBSTITUENTS
CARBON-CARBON COVALENT BONDS CAN BE SINGLE, DOUBLE OR TRIPLE DIFFERENT ATOMS / GROUPS OF ATOMS CAN BE PLACED ON THE CARBONS The basic atom is HYDROGEN but groups containing OXYGEN, NITROGEN, HALOGENS and SULPHUR are very common. CARBON SKELETON FUNCTIONAL CARBON SKELETON FUNCTIONAL GROUP GROUP The chemistry of an organic compound is determined by its FUNCTIONAL GROUP

MULTIPLE BONDING AND SUBSTITUENTS
THE SPECIAL NATURE OF CARBON MULTIPLE BONDING AND SUBSTITUENTS ATOMS/GROUPS CAN BE PLACED IN DIFFERENT POSITIONS ON A CARBON SKELETON THE C=C DOUBLE BOND IS IN A DIFFERENT POSITION PENT-1-ENE PENT-2-ENE THE CHLORINE ATOM IS IN A DIFFERENT POSITION 1-CHLOROBUTANE CHLOROBUTANE

Classification of Organic Compounds
Hydrocarbons : Compounds containing carbon and hydrogen only Non-hydrocarbons : Compounds that may also contain other elements such as nitrogen, sulphur, halogen or oxygen atoms besides hydrogen and carbon.

Homologous Series A series of compounds with the same general formula (e.g. Alkanes CnH2n+2) and functional group (e.g. C=C, OH) Each member differs from the next by CH2 Members have the same chemical properties. Members show a gradation in physical properties.

Some functional groups
Homologous Series Condensed structural formula Structure of Functional Group Alkanes -CH2CH2- Alkenes -CH=CH- C = C Halogenoalkanes -X ( X = F, Cl, Br, I) Alcohols -OH O H Aldehydes -CHO O C H Ketones -CO- R C=O R’ Carboxylic acids -COOH

alkene alcohol ketone ester carboxylic acid

carboxylic acid ester aldehyde ether amine nitrile Page 425

Influence of functional groups
bonding and shape type and strength of intermolecular forces physical properties nomenclature chemical reactivity

Solubility in water Homologous Series Polarity Intermoecular forces
Boiling point Solubility in water Alkane non-polar van der Waals’ low Insoluble Alkene Alcohol Lower members soluble; H bonding to water Aldehydes/ ketones Dipole-dipole > alkane < alcohol Lower members soluble; polar and water can H bond with them. Carboxylic acid Hydrogen bonding High > alcohol (more H bonding) Halogenoalkane For same no. of C atoms, I > Br > Cl Van der Waals’ forces stronger if Mris higher All missing polarity from alcohol to halogenoalkane is polar. Alcohol – intermolecular force is hydrogen bonding Halogenoalkane – intermolecular force is dipole-dipole Alkene – boiling pt is low Alcohol – boiling pt is high

Isomerism 1st isomer 2nd isomer
Structural Isomers are 2 or more compounds with the same molecular formula but different structural formula. Example : Isomers of butane 1st isomer nd isomer Condensed CH3CH2CH2CH CH3CH(CH3)CH3 formula (has a branched chain)

Pentane has 3 isomers: 1st isomer 2nd isomer 3rd isomer Condensed
formula

Some isomers of C5H12O -OH attached to C-1 OH attached to C-2
Many more isomers of alcohol. Some are not alcohol. E.g. ether containing C-O-C as a fn’al group. CH3CH2CH2OCH2CH2CH3 Page 428 Practice Qns

Physical Properties of Alkanes
First 4 members are gases at room temperature & pressure (r.t.p.) All members are insoluble in water but soluble in organic solvent. Reasons: Made up of covalent molecules held by weak intermolecular forces, so less energy is required to overcome the forces to separate the molecules. Like dissolve like Do you expect isomers to have similar physical properties?

Isomers have different physical properties e. g
Isomers have different physical properties e.g. boiling point or melting point because the different structures will affect the physical properties. Isomers have the same chemical properties because there are the same number and kind of atoms in each isomer.

A systematic name has two main parts.
I.U.P.A.C. NOMENCLATURE A systematic name has two main parts. STEM number of carbon atoms in longest chain bearing the functional group + a prefix showing the position and identity of any side-chain substituents. Prefix C atoms Alkane meth- 1 methane eth- 2 ethane prop- 3 propane but- 4 butane pent- 5 pentane hex- 6 hexane hept- 7 heptane oct- 8 octane non- 9 nonane dec decane Apart from the first four, which have trivial names, the number of carbons atoms is indicated by a prefix derived from the Greek numbering system. The list of alkanes demonstrate the use of prefixes. The ending -ane is the same as they are all alkanes. Working out which is the longest chain can pose a problem with larger molecules.

I.U.P.A.C. NOMENCLATURE CH3 CH3 CH2 CH2 CH2 CH3 CH2 CH3
How long is a chain? Because organic molecules are three dimensional and paper is two dimensional it can be confusing when comparing molecules. This is because... 1. it is too complicated to draw molecules with the correct bond angles 2. single covalent bonds are free to rotate All the following written structures are of the same molecule - PENTANE C5H12 CH2 CH3 CH2 CH3 CH3 CH2 CH2 CH3 A simple way to check is to run a finger along the chain and see how many carbon atoms can be covered without reversing direction or taking the finger off the page. In all the above there are... FIVE CARBON ATOMS IN A LINE.

How long is the longest chain?
I.U.P.A.C. NOMENCLATURE How long is the longest chain? Look at the structures and work out how many carbon atoms are in the longest chain. CH2 CH3 CH THE ANSWERS ARE ON THE NEXT SLIDE CH2 CH3 CH CH3 CH CH2

How long is the longest chain?
I.U.P.A.C. NOMENCLATURE How long is the longest chain? Look at the structures and work out how many carbon atoms are in the longest chain. CH2 CH3 CH LONGEST CHAIN = 5 CH2 CH3 CH LONGEST CHAIN = 6 CH3 CH CH2 LONGEST CHAIN = 6

A systematic name has two main parts. 1-CHLOROBUTANE 2-CHLOROBUTANE
I.U.P.A.C. NOMENCLATURE A systematic name has two main parts. SUFFIX An ending that tells you which functional group is present See if any functional groups are present. Add relevant ending to the basic stem. In many cases the position of the functional group must be given to avoid any ambiguity Functional group Suffix ALKANE - ANE ALKENE - ENE ALKYNE - YNE ALCOHOL - OL ALDEHYDE - AL KETONE - ONE ACID - OIC ACID 1-CHLOROBUTANE CHLOROBUTANE SUBSTITUENTS Many compounds have substituents (additional atoms, or groups) attached to the chain. Their position is numbered.

I.U.P.A.C. NOMENCLATURE SIDE-CHAIN carbon based substituents are named before the chain name. they have the prefix -yl added to the basic stem (e.g. CH3 is methyl). Number the principal chain from one end to give the lowest numbers. Side-chain names appear in alphabetical order butyl, ethyl, methyl, propyl Each side-chain is given its own number. If identical side-chains appear more than once, prefix with di, tri, tetra, penta, hexa Numbers are separated from names by a HYPHEN e.g methylheptane Numbers are separated from numbers by a COMMA e.g. 2,3-dimethylbutane Alkyl radicals methyl CH CH3 ethyl CH3- CH C2H5 propyl CH3- CH2- CH C3H7

I.U.P.A.C. NOMENCLATURE CH3 CH2 CH
SIDE-CHAIN carbon based substituents are named before the chain name. they have the prefix -yl added to the basic stem (e.g. CH3 is methyl). Number the principal chain from one end to give the lowest numbers. Side-chain names appear in alphabetical order butyl, ethyl, methyl, propyl Each side-chain is given its own number. If identical side-chains appear more than once, prefix with di, tri, tetra, penta, hexa Numbers are separated from names by a HYPHEN e.g methylheptane Numbers are separated from numbers by a COMMA e.g. 2,3-dimethylbutane Example longest chain 8 (it is an octane) 3,4,6 are the numbers NOT 3,5,6 order is ethyl, methyl, propyl 3-ethyl-5-methyl-4-propyloctane Alkyl radicals methyl CH CH3 ethyl CH3- CH C2H5 propyl CH3- CH2- CH C3H7 CH3 CH2 CH

I.U.P.A.C. NOMENCLATURE CH2 CH3 CH CH2 CH3 CH CH3 CH CH2
Apply the rules and name these alkanes THE ANSWERS ARE ON THE NEXT SLIDE CH2 CH3 CH CH2 CH3 CH CH3 CH CH2

Apply the rules and name these alkanes
I.U.P.A.C. NOMENCLATURE I.U.P.A.C. NOMENCLATURE Apply the rules and name these alkanes CH2 CH3 CH CH2 CH3 CH CH3 CH CH2

I.U.P.A.C. NOMENCLATURE I.U.P.A.C. NOMENCLATURE Apply the rules and name these alkanes Longest chain = 5 so it is a pentane A CH3, methyl, group is attached to the third carbon from one end... 3-methylpentane CH2 CH3 CH CH2 CH3 CH CH3 CH CH2

I.U.P.A.C. NOMENCLATURE I.U.P.A.C. NOMENCLATURE Apply the rules and name these alkanes Longest chain = 5 so it is a pentane A CH3, methyl, group is attached to the third carbon from one end... 3-methylpentane CH2 CH3 CH Longest chain = 6 so it is a hexane A CH3, methyl, group is attached to the second carbon from one end... 2-methylhexane CH2 CH3 CH CH3 CH CH2

I.U.P.A.C. NOMENCLATURE I.U.P.A.C. NOMENCLATURE Apply the rules and name these alkanes CH2 CH3 CH Longest chain = 5 so it is a pentane A CH3, methyl, group is attached to the third carbon from one end... 3-methylpentane Longest chain = 6 so it is a hexane A CH3, methyl, group is attached to the second carbon from one end... 2-methylhexane CH2 CH3 CH Longest chain = 6 so it is a hexane CH3, methyl, groups are attached to the third and fourth carbon atoms (whichever end you count from). 3,4-dimethylhexane CH3 CH CH2 Discuss examples Page 430

Name the following hydrocarbons:
C(CH3)4 CH3CH(C2H5)CH3 CH3CH2CH(C2H5)CH2CH3

Alkanes Belongs to the homologous series of saturated hydrocarbons
Contain only single covalent bonds between atoms in molecules. Contain only hydrogen and carbon atoms

Alkanes Alkanes  hydrocarbons that contain only single bonds
Each one different from previous by 1 C and 2 H

General Characteristics
Can be represented by a general formula. Physical property changes gradually as the number of CH2 group increases. Have similar chemical properties (since they have the same functional groups)

For alkanes with 3 or less C atoms, only 1 molecular structure possible
In alkanes with more than 3, chains can be straight or branched So, alkanes with 4 or more C have structural isomers

Full structural formula
Alkanes Names Molecluar Formula Mr Empirical Formula Condensed Formula Bpt /0 C State Full structural formula Methane CH4 16 -164 Gas Ethane 30 -89 Propane C3H8 44 CH3CH2CH3 -42 Butane 58 -0.5 Pentane C5H12 72 +36 Liquid Hexane C6H14 CH3 (CH2) 4CH3 liquid Non-polar nature, the intermolecular forces between the molecules are solely van der waals forces. These forces are based on the interactions between temporary dipoles created by momentary shifts in electrons distribution. The strength of the forces is related to the no. Of electrons involved in the structure and the SA of the molecules over which the interactions can be spread.Increasing the chain length of the molecules increase both these features and so the strength of teh van der Waals’ forces increases with the incraesing molecuar size. Physical properties dependent on these interactions, such as mpt, bpt and enthalpy of vaporisation will also increase with the length of chain. Name ends with –ane and has a general molecular formula CnH2n+2

Physical states Alkanes with lowest molecular mass (1-4 C atoms) are gases Natural gas fossil fuel made primarily of alkanes containing 1-4 C atoms C-H bonds are nonpolar Only forces of attraction between nonpolar molecules are weak intermolecular forces

The strength of the forces is related to the no
The strength of the forces is related to the no. of electrons involved in the structure and the surface area of the molecules over which the interactions can be spread. Increasing the chain length of the molecules increase both these features and so the strength of the van der Waals’ forces increases with the increasing molecuar size. Physical properties dependent on these interactions, such as mpt, bpt and enthalpy of vaporisation will also increase with the length of chain. Non-polar nature, the intermolecular forces between the molecules are solely van der waals forces. These forces are based on the interactions between temporary dipoles created by momentary shifts in electrons distribution. The strength of the forces is related to the no. Of electrons involved in the structure and the SA of the molecules over which the interactions can be spread.Increasing the chain length of the molecules increase both these features and so the strength of teh van der Waals’ forces increases with the incraesing molecuar size. Physical properties dependent on these interactions, such as mpt, bpt and enthalpy of vaporisation will also increase with the length of chain.

Larger alkanes are liquid
Gasoline, kerosene made mostly of liquid alkanes Stronger forces hold together enough to form liquids Alkanes with very high molecular mass are solid Paraffin wax contains solid alkanes (candles)

Boiling points Increase with increasing molecular mass
As the strength of the van der Waals’ forces increases, more energy (heat) required to break them This property used in separation of petroleum (major source of alkanes) Petroleum  complex mixture of different hydrocarbons that varies greatly in composition

Separation of Petroleum
Petroleum is a mixture of hydrocarbon molecules from 1 to more than 50 C atoms is heated in a furnace. Oil vaporizes and passes up the fractionating column. The different fractions come out of the column at different heights depending on their boiling points. Substances with low boiling points are collected near the top of the column A hydrocarbon with a long chain has __________________than one with a shorter carbon chain higher boiling point

General Properties As the no. of C atoms increases,
Fractions Boiling (0C) Approx no. of C atoms Petroleum gas Below 40 1-4 Petrol (gasoline) 40-75 5-10 Naphtha 75-150 7-14 Kerosene (paraffin) 11-16 Diesel Oil 16-20 Lubricating Oil 20-35 Bitumen Above 350 More than 70 As the no. of C atoms increases, boiling point increases liquids are more viscous liquids burn less easily

Cracking To meet the demands for fractions like petrol and kerosene, a process called cracking is carried out. This involves the use of high temperature, pressure and catalyst to split the larger molecules (of higher boiling points) into smaller ones (of lower boiling points) Example C10H2  C10H C10H22

Alkenes Belongs to the homologous series of unsaturated hydrocarbons.
Contains double covalent bonds between C atoms in molecules. Contain only H and C atoms. Draw the dot and cross diagram of ethene

Alkenes Name formula Mr Full structural formula Ethene C2H4 28
Pro-1-pene C3H6 42 But-1-ene C4H8 56 Pent-1-ene C5H10 70 Hex-1-ene Important plant hormone – induces flowering and ripening of fruit

Isomerism Butene has 3 isomers: 1st isomer 2nd isomer 3rd isomer
Condensed formula

Draw all the isomers of C5H10 and write their condensed formulae.
Page 440

NAMING ALKENES Length In alkenes the principal chain is not always the longest chain It must contain the double bond the name ends in -ENE Position Count from one end as with alkanes. Indicated by the lower numbered carbon atom on one end of the C=C bond CH3CH2CH=CHCH3 is pent-2-ene (NOT pent-3-ene) Side-chain Similar to alkanes position is based on the number allocated to the double bond CH2 = CH(CH3)CH2CH CH2 = CHCH(CH3)CH3 2-methylbut-1-ene 3-methylbut-1-ene

Naming alkenes (more than 1 C=C)
Page 440

Name the following alkenes: (a) (b) CH3CH2CH(CH3)CH= CH2
(c) (d) CH2= C(CH3)CH2CH= CH2 (c) 4-methyl-1,3-pentadiene

Alcohols general formula CnH2n+1OH or R-OH
Name formula Full structural formula Methanol Ethanol C 2H5OH Propan-1-ol C3H7OH Butan-1-ol C4H9OH Pentan-1-ol general formula CnH2n+1OH or R-OH Lower members are very soluble in water because of hydrogen bonding

Alcohols Alcohols are the homologous series with the general formula CnH2n+1OH. They all contain the functional group, OH, which is called the hydroxyl group. Alcohols can be classified as primary, secondary or tertiary, depending on the carbon skeleton to which the hydroxyl group is attached.

1 alkyl group on C next to OH so primary alcohol, 1° R2CHOH
2 alkyl groups on C next to OH so secondary alcohol, 2° R3COH 3 alkyl groups on C next to OH so tertiary alcohol, 3° Draw out the structure, name and classify all the alcohols with the formula C4H9OH.

OH H C Butan-1-ol primary OH H C Butan-2-ol secondary

OH H C CH3 OH H C CH3 2-methylpropan-1-ol primary
2-methylpropan-2-ol tertiary Page 448

Draw the isomers of propanol.

Aldehydes (Carbonyl compound)
Name formula Full structural formula Methanal HCHO Ethanal CH3CHO Propanal C2H5CHO Butanal general formula CnH2n+1CHO or R-CHO

Name and draw the full structural formula of
CH3CH2CH2CH(CH3)CHO

Ketones general formula R-CO-R’ where R’ represents either
Name formula Full structural formula Propanone CH3COCH3 Butanone CH3COC2H5 general formula R-CO-R’ where R’ represents either The same alkyl group as R or a differen alkyl group

Draw the full structural formula of pentan-2-one and write its condensed formula.

Physical properties of aldehydes and ketones
Aldehydes and ketones have very similar boiling points. Aldehyde has higher b. pt. than alkane of similar RMM and lower b. pt. than alcohols of similar RMM.

Aldehydes are polar due to the very electronegative O, whereas alkanes are nonpolar.
IMF between aldehyde molecules are stronger than those in alkane of similar RMM due to dipole-dipole interaction but only van der Waals forces are present between alkane molecules. Hence aldehydes have higher bpt than alkanes. Alcohols are polar and its O is joined directly to H – able to form H bonding. Since strength of hydrogen bond > dipole- dipole interaction, alcohol has higher bpt than aldehydes.

Solubility Lower members (methanal, ethanal, propanal, propanone, butanone) are soluble in water since they form H bonding with water. Aldehyde cannot H bond to each other but able to form H bond with water. Solubilty decreases with increasing length of HC chains because of the non-polar nature of the HC chain.

Carboxylic acids general formula R-COOH or R-CO2H Name formula
Full structural formula Methanoic acid HCOOH Ethanoic acid CH3COOH Propanoic acid C2H5COOH general formula R-COOH or R-CO2H

Name the following organic compound and write its condensed formula.
Practice Page 455

Physical properties of carboxylic acids
Carboxylic acids have H bonding between molecules. They have higher bpt. than aldehydes and alcohols of similar RMM. Carboxylic acids have two O atoms per molecule, hence have stronger H bonding than alcohols which has only one O atom per molecule. Therefore, carboxylic acids have higher bpt. than alcohols. Carboxylic acids with lower RMM are generally soluble in water and less soluble when the HC chain increases.

Halogenoalkanes Named by using name of the alkane from which they are derived with the prefix chloro- , bromo- or iodo-. For example: CH3CH2Br is bromoethane (CH3)2CHCH2Cl is 1-chloro-2-methylpropane

Remember the position of the halogen atom must be indicated using the appropriate number so
CH3CH2CH2Cl is 1-chloropropane and CH3CHClCH3 is 2-chloropropane Halogenoalkanes can be classified in the same way as alcohols.

Halogenoalkanes (halogen atom as fn’al group)
Name formula Full structural formula Iodomethane 1-bromo-3-fluoro-pentane general formula R-X where X = F, Cl, Br or I

Primary, secondary and tertiary halogenoalkanes
Page 458

C X C X where X = Cl, Br or I Key feature of halogenoalkanes is
What is notable about this bond compared with say, C – C and C – H? The halogen atom is more electronegative than C so the bond is polarised: C X + -

C Cl C Br C I ORDER OF BOND POLARITIES: > >
+ - + - + - C Cl > C Br > C I So is order of reactivity: chloroalkane > bromoalkanes > iodoalkanes? Is there another factor that ought to be considered before reaching a conclusion? BOND ENERGIES

This suggests that the order of reactivity is:
Bond energies: Bond Bond energy in kJmol-1 C - Cl C - Br C - I 346 290 234 This suggests that the order of reactivity is: iodoalkane > bromoalkanes > chloroalkanes

Boiling points No. of C atoms
Halogenoalkanes have higher bpt. than alkanes with the same no. of C atoms. Due to the higher RMM and hence stronger van der Waals’ forces. Refer to table Page 456

Compounds of same RMM Bromo- and iodo-compounds have substantially lower bpt. than alkanes of similar RMM. Alkanes have longer chain molecules – in the liquid state – more S. A. Of molecules in contact – stronger IMF. Little difference between bpt of alkanes and chloroalkanes of similar RMM. The chloroalkanes are polar but alkanes are non-polar – expect to have higher bpt but is balanced out by the long HC chain of alkanes. Refer to table Page 456

Solubility Sparingly soluble or insoluble in water
Soluble in organic solvent

Amines Strong smelling substances general formula R-NH2 Page 465 Name
Full structural formula Methylamine 2-aminobutane general formula R-NH2 Strong smelling substances Page 465

Esters general formula R-COOR’, where R’ is an alkyl group Name
Full structural formula Methyl methanoate Propyl ethanoate general formula R-COOR’, where R’ is an alkyl group

Aromatic compounds (arenes)
Name formula Full structural formula Benene C6H6 Methyl benzene

Primary, secondary and tertiary compounds
Are the following molecules primary, secondary or tertiary? 3-methylpentan-3-ol Pentan-2-ol 1-chlorobutane

Are the following molecules primary, secondary or tertiary?
3-methylpentan-3-ol Pentan-2-ol 1-chlorobutane

Additional notes

Intermolecular forces
also referred to as noncovalent interactions or nonbonded interactions. several types of intermolecular interactions.

Physical Properties of Organic Molecules
What type of intermolecular force would you expect to find between alkanes, halogenoalkanes, aldehydes, ketones, alcohols and carboxylic acids? Use this information to deduce the relative boiling points of these homologous series and their solubility in water.

Ion-ion interactions Ionic compounds contain oppositely charged particles held together by extremely strong electrostatic interactions. These ionic interactions are much stronger than the intermolecular forces present between covalent molecules.

Van der Waals’ forces (London forces)
are weak interactions caused by momentary changes in electron density in a molecule. the only attractive forces present in nonpolar compounds. Even though CH4 has no net dipole, at any one instant its electron density may not be completely symmetrical, resulting in a temporary dipole. This can induce a temporary dipole in another molecule. The weak interaction of these temporary dipoles constituents van der Waals forces.

van der Waals forces are also affected by polarizability.
Polarizability is a measure of how the electron cloud around an atom responds to changes in its electronic environment. Larger atoms, like iodine, which have more loosely held valence electrons, are more polarizable than smaller atoms like fluorine, which have more tightly held electrons. Thus, two F2 molecules have little attractive force between them since the electrons are tightly held and temporary dipoles are difficult to induce.

Hydrogen bonding Hydrogen bonding typically occurs when a hydrogen atom bonded to O, N, or F, is electrostatically attracted to a lone pair of electrons on an O, N, or F atom in another molecule.

Physical properties – Boiling points
In boiling, energy is needed to overcome the attractive forces in the more ordered liquid state. The stronger the intermolecular forces, the higher the boiling point. For compounds with approximately the same molecular weight:

Consider the examples below which illustrate the effect of
size and polarizability on boiling points.

In summary The intermolecular forces increase with increasing polarization of bonds. Strength of forces (and therefore impact on boiling points) is ionic > hydrogen bonding > dipole dipole > van der Waals’ forces Boiling point increases with molecular weight, and with surface area.

Volatility A measure of how easily a substance evaporates. A high volatile substance evaporates easily and has a low boiling point. 3 factors that affect the volatility Volaility decreases with the increasing molecular size. The longer molecule with increased molecular size has stronger van der Waals’ force between the molecules, hence increasing boiling point. Hence, the early molecules are gases and liquids while the later molecules are mostly soilds.

A branched isomer of the compound is likely to have a lower boiling point than its straight chain isomer. The branching of a chain results in a more spherical overall shape to the molecule. This means there is less contact surface area between molecules and these branched isomers have weaker intermolecular forces and hence lower boiling points.

The nature of the functional group present will influence the volatiity, depending on the effect of intermolecular forces. Polar groups will have stronger dipole-dipole interactions between molecules hence higher boiling points. Groups that are capable of forming hydogen bonds will result in even stronger forces between the molecules, giving rise to even higher boiling points.

Melting point In melting, energy is needed to overcome the attractive forces in the more ordered crystalline solid. The stronger the intermolecular forces, the higher the melting point. Given the same functional group, the more symmetrical the compound, the higher the melting point.

The trend in melting points of pentane, butanal, and 1-butanol parallels the trend observed in their boiling points.

Solubility Solubility is the extent to which a compound, called a solute, dissolves in a liquid, called a solvent. In dissolving a compound, the energy needed to break up the interactions between the molecules or ions of the solute comes from new interactions between the solute and the solvent.

An organic compound is water soluble only if it contains one polar functional group capable of hydrogen bonding with the solvent for every five C atoms it contains. For example, compare the solubility of butane and acetone in H2O and CCl4.

To dissolve an ionic compound, the strong ion-ion interactions must be replaced by many weaker ion-dipole interactions.

The nonpolar part of a molecule that is not attracted to H2O is said to be hydrophobic.
The polar part of a molecule that can hydrogen bond to H2O is said to be hydrophilic. In cholesterol, for example, the hydroxy group is hydrophilic, whereas the carbon skeleton is hydrophobic.

Soap Soap molecules have two distinct parts—a hydrophilic
portion composed of ions called the polar head, and a hydrophobic carbon chain of nonpolar C—C and C—H bonds, called the nonpolar tail.

Influence of functional groups on reactivity

On the other hand, alkyl halides possess an electrophilic carbon atom, so they react with electron rich nucleophiles.

Organic Chemistry.

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