Z5e Chapter 22 Organic Chemistry

2 Z5e 22.1 Alkanes: Saturated Hydrocarbons  Carbon atoms can form 4 bonds  Nitrogen atom can form 3 bonds  Oxygen atoms can form 2 bonds  Hydrogen atoms can form 1 bond  Useful to know when building up structures  Double and triple bonds count as one “effective” pair.

3 Examples of Isomers The formula C 4 H 10 has two different structures CH 3 CH 3 CH 2 CH 2 CH 3 CH 3 CHCH 3 Butane 2-methylpropane When a CH 3 is is used to form a branch, it makes a new isomer of C 4 H 10.

4 Structural Isomers l Compounds that have the same molecular formula, but different molecular structures, are called structural isomers l Butane and 2-methylpropane in previous slide. l Also have different properties, such as b.p., m.p., and reactivity

5 Geometric Isomers l There is a lack of rotation around a carbon to carbon multiple bond –has an important structural implication –Two possible methyl arrangements: 1. trans configuration - substituted groups on opposite sides of double bond 2. cis configuration - same side

6 Geometric Isomers l Differ only in the geometry of their substituted groups l Like other structural isomers, have different physical and chemical properties

7 Geometric Isomers of 1,2-dichloroethene l Cl ClH Cl C=C C=C H HCl H cistrans l Rigid structure so these are isomers with different properties.

8 Geometric Isomers of chloroethene? l H ClH H C=C C=C H HH Cl l Rigid structure BUT both carbons do NOT have two DIFFERENT groups attached to them. l These are just rotated in space, but are the same.

9 Nongeometric versions of 1,2- dichloroethene l Cl ClH Cl C--C C--C H HCl H l Non-rigid structure so these are NOT isomers.

10 Branched-Chain Alkanes l Rules for naming - page Longest chain is the parent (tricky). 2. Number so branches have low # of carbons. 3. Give position number to branch 4. Use prefixes if more than one branch 5. Alphabetize branches 6. Use proper punctuation ( -, )

11 Naming Alkenes l Find longest parent that has the double bond in it l New ending: -ene l Number the chain, so that the double bond gets the lower number l Name and number the substituents l Samples on page 1069

12 Naming Aromatic Compounds Aromatic compounds are named with benzene as the parent chain. One side group is named in front of the name benzene. methylbenzenechlorobenzene (toluene)

13 Naming Aromatic Compounds When two groups are attached to benzene, the ring is numbered to give the lower numbers to the side groups. The prefixes ortho (1,2), meta (1,3-) and para (1,4-) are also used.

14 Some Common Names Some substituted benzene rings also use a common name. Then naming with additional more side groups uses the ortho-, meta-, para- system.

15 Z5e 1077 Table 22.5 Common Functional Groups

16 Alcohols l Alcohols - a class of organic compounds with an -OH group –The -OH functional group in alcohols is called a “hydroxyl” group; thus R-OH is the formula l How is this different from the hydroxide ion? l The hydroxyl group is covalently bonded to the R group. Hydroxides have ionic bonding with their cations.

17 Alcohols l Common names: –similar to halocarbons: Name the alkyl group followed by the word alcohol –One carbon alcohol = methyl alcohol

18 Alcohols l Arranged into categories according to the number of R groups attached to the carbon with the hydroxyl –1 R group: primary alcohol –2 R groups: secondary alcohol –3 R groups: tertiary alcohol l Let’s do some examples on the whiteboard (see p. 1077).

19 Naming Alcohols A carbon compound that contain -OH (hydroxyl) group A carbon compound that contain -OH (hydroxyl) group In IUPAC name, the -e in alkane name is replaced with -ol. In IUPAC name, the -e in alkane name is replaced with -ol. Parent is the longest chain containing the carbon with the hydroxly attached. Parent is the longest chain containing the carbon with the hydroxly attached. CH 4 methane CH 3 OH methanol (methyl alcohol) CH 3 CH 3 ethane CH 3 CH 2 OH ethanol (ethyl alcohol )

20 Alcohols l The hydroxyl is given the lowest position number l Alcohols containing 2, 3, and 4 of the -OH substituents are named diols, triols, and tetrols respectively

21 More Names of Alcohols IUPAC names for longer chains number the chain from the end nearest the -OH group. CH 3 CH 2 CH 2 OH1-propanol OH CH 3 CHCH 3 2-propanol CH 3 OH CH 3 CHCH 2 CH 2 CHCH 3 5-methyl-2-hexanol

22 Ethers l Contain an -O- between two carbon groups l Simple ethers named from -yl names of the attached groups and adding ether. l Naming? The two R groups are alphabetized, and followed by ether l Two R groups the same? Use the prefix di. CH 3 -O-CH 3 dimethyl ether CH 3 -O-CH 2 CH 3 ethyl methyl ether

23 Aldehydes and Ketones l Review: –alcohol has an oxygen bonded to a carbon group and a hydrogen –ether has an oxygen bonded to two carbon groups l An oxygen can also be bonded to a single carbon by a double bond

24 Aldehydes and Ketones l The C=O group is called the “carbonyl group” –it is the functional group in both aldehydes and ketones l Aldehydes - carbonyl group always joined to at least one hydrogen (meaning it is always on the end!) l R C H O

25 Aldehydes and Ketones l Ketones - the carbon of the carbonyl group is joined to two other carbons (meaning it is never on the end) l R C R O l See structures on pp

26 Aldehydes and Ketones In an aldehyde, an H atom is attached to a carbonyl group Ocarbonyl group  CH 3 -C-H In a ketone, two carbon groups are attached to a carbonyl group Ocarbonyl group  CH 3 -C-CH 3

27 Naming Aldehydes and Ketones l Aldehydes: identify longest chain containing the carbonyl group, then the -e ending replaced by -al l methanal, ethanal, etc. l ketones: longest chain w/carbonyl, then new ending of -one; number it l propanone, 2-pentanone, 3-pentanone

28 Naming Aldehydes IUPAC: Replace the -e in the alkane name -al Common: Add aldehyde to the prefixes form (1C), acet (2C), propion(3), and butry(4C) O O O    H-C-H CH 3 -C-H CH 3 CH 2 C-H methanalethanal propanal (formaldehyde) (acetaldehyde) (propionaldehyde)

29 Naming Ketones In the IUPAC name, the -e in the alkane name is replaced with -one In the common name, add the word ketone after naming the alkyl groups attached to the carbonyl group O O  CH 3 -C-CH 3 CH 3 -C-CH 2 -CH 3 Propanone 2-Butanone (Dimethyl ketone) (Ethyl methyl ketone)

30 Aldehydes and Ketones l Neither can form intermolecular hydrogen bonds, thus a much lower b.p. than corresponding alcohols l Wide variety have been isolated from plants and animals; possible fragrant odor or taste; many common names

31 Carboxylic Acids l Also have a carbonyl group (C=O) like aldehydes and keytones, but is also attached to a hydroxyl group (- OH) = “carboxyl” group l general formula: R-COOH –weak acids (ionize slightly) l Named by replacing -e with -oic and followed by the word acid l methanoic acid; ethanoic acid

32 Carboxyl Group Carboxylic acids contain the carboxyl group on carbon 1. O  CH 3 — C—OH= CH 3 —COOH carboxyl group

33 Carboxylic Acids - look for functional group

34 Naming Rules l Identify longest chain l (IUPAC) Number carboxyl carbon as 1 l (Common) Assign , ,  to carbon atoms adjacent to carboxyl carbon CH 3 | CH 3 — CH—CH 2 —COOH IUPAC 3-methylbutanoic acid Common  -methylbutryic acid

35 Naming Carboxylic Acids Formula IUPAC Common alkan -oic acid prefix – ic acid HCOOH methanoic acid formic acid CH 3 COOH ethanoic acid acetic acid CH 3 CH 2 COOH propanoic acid propionic acid CH 3 CH 2 CH 2 COOH butanoic acid butyric acid

36 Esters In and ester, the H in the carboxyl group is replaced with an alkyl group O  CH 3 — C—O —CH 3 = CH 3 —COO —CH 3 ester group

37 Esters l General formula: RCOOR l Derivatives of carboxylic acids, where the -OH from the carboxyl group is replaced by an -OR from an alcohol: carboxylic acid + alcohol  ester + water l Usually a trace of mineral acid added as catalyst (because acids are dehydrating agents) l many esters have pleasant, fruity odors- banana, pineapple, perfumes l Lab 22 was an ester lab.

38 Esters l Although polar, they do not form hydrogen bonds (reason: there is no hydrogen bonded to a highly electronegative atom) –thus, much lower b.p. than the hydrogen-bonded carboxylic acids they came from!

39 Naming Esters l Naming? It has 2 words: l 1st: Name the alkyl attached to the single bonded oxygen from the alcohol. l 2nd: take the acid name, remove the -oic acid, add -oate. l O CH 3 CH 2 C O CH 2 CH 3 l Ethyl propanoate

40 Naming Esters l Name the alkyl from the alcohol –O- l Name the acid with the C=O with –ate acidalcohol O  methyl CH 3 — C—O —CH 3 Ethanoate methyl ethanoate (IUPAC) (acetate)methyl acetate (common)

41 Amines l Organic compounds of nitrogen N l Classified as primary, secondary, tertiary CH 3 CH 3   CH 3 —NH 2 CH 3 —NH CH 3 —N — CH 3 1° 2° 3°

42 Naming Amines IUPAC aminoalkane Common alkylamine CH 3 CH 2 NH 2 CH 3 —NH —CH 3 aminoethane N-methylaminomethane (ethylamine) (dimethylamine) NH 2 | CH 3 CHCH 3 2-aminopropane (isopropylamine) Aniline N-methylaniline

43 Substitution Reactions l Halogens on carbon chains are readily displaced by hydroxide ions (OH 1- ) to make an alcohol + a salt: R-X + OH 1-  R-OH + X 1-

44 Substitution Reactions CH 3 -I + KOH  CH 3 -OH + KI CH 3 CH 2 Br + NaOH  CH 3 CH 2 OH + NaBr IodomethaneMethanol BromoethaneEthanol

45 Addition Reactions l Carbon-carbon single bond is not easy to break l In double bonded alkenes, it is easier to break a bond l Addition reaction- substance is added at the double or triple bond location, after it is broken l CH 3 CH=CHCH 3 + H 2  CH3CH 2 CH 2 CH3

46 Condensation Reactions l Two molecules combine l Acid + Alcohol  Ester + water l HCOOH + HOCH 3  HCOOCH 3 + H 2 O

47 Elimination Reactions l A simple molecule like water or ammonia is removed from an organic molecule.

48 Condensation Polymer l Polymer formed by molecules of two different compounds joining to form the large molecule l One compound usually has an amine functional group l Other molecule has carboxylic acid functional group l Split out water molecule to form peptide linkage O H C N

49 Condensation to Nylon Monomers - hexanediamine & adipic acid Polyamide - amide (peptide) is in the polymer Nylon 66 - each monomer has 6 carbon atoms Polyester is another type of condensation polymer