1559T_ch17_304-32211/3/0510:48Page308 EQA 308.Chapter 17 ALDEHYDES AND KETONES:THE CARBONYL GROUF Solutions to Problems 20.(a 2-Butanone 5-Methyl-3-bexanone 3.3-Dimethyl-2-bu 0 2.4-Dimethyl-3-pentano 1-Phenylethanone 1-(3-NitrophenyD)etha 21.(a)2.4-Dimethyl-3-pentanone (b)4-Methyl-3-phenylpentanal (c）3-Buten-2-one (d)trans-4-Chloro-3-butenal (e)4-Bromo-2-cyclopentenone CH:- (g) C=C-CH CH H-C 22.Degrees of unsaturation for.H=16+2-18:degrees of unsaturation==3 bonds or rings present. (a)C:Molecule containsC=0(=198.6)andC=C=139.8 and 140.7). 'H:Obvious features include =2.15(s.3 H).for CHC-.and 8=6.78(t.1 H).for Xe-c Note the absence of any other alkene hydrogens.So we can start with these pieces 6-cc adding up to CsHo Still needed are three more C's.six more H's,and another degree of unsaturation,which will have This is not the only possible answer,but it is the actual molecule that gives the indicated spectra Solutions to Problems 20. (a) (b) (c) (d) (e) (f) 21. (a) 2,4-Dimethyl-3-pentanone (b) 4-Methyl-3-phenylpentanal (c) 3-Buten-2-one (d) trans-4-Chloro-3-butenal (e) 4-Bromo-2-cyclopentenone (f) cis-2-Ethanoyl-3-phenylcyclohexanone (cis-2-acetyl-3-phenylcyclohexanone) (g) (h) 22. Degrees of unsaturation for C8H12O, Hsat 16
2 18; degrees of unsaturation  (18 2  12) 3  bonds or rings present. (a) 13C: Molecule contains ( 198.6) and ( 139.8 and 140.7). O B 1 H: Obvious features include  2.15 (s, 3 H), for CH3CO, and  6.78 (t, 1 H), for . Note the absence of any other alkene hydrogens. So we can start with these pieces: O B CH3OCO and , adding up to C5H6O Still needed are three more C’s, six more H’s, and another degree of unsaturation, which will have to be a ring. A simple way to put together a trial structure would be to finish a six-membered ring with three CH2 groups, and then attach the acetyl group: This is not the only possible answer, but it is the actual molecule that gives the indicated spectra. O CH3 H CH2 C C H CH2 C C C O C C CH O Cl CH3 H C CH3 C C C H O O O NO2 1-(3-Nitrophenyl)ethanone O 1-Phenylethanone O 2,4-Dimethyl-3-pentanone O 3,3-Dimethyl-2-butanone O 5-Methyl-3-hexanone O 2-Butanone 308 • Chapter 17 ALDEHYDES AND KETONES: THE CARBONYL GROUP 1559T_ch17_304-322 11/3/05 10:48 Page 308