Problem 1
Draw structures for (a) pentanal, (b) benzaldehyde, (c) butanone, (d) heptan-3-one, (e) pentanoic acid, (f) pentanoyl chloride; (g) ethyl propanoate, (h) phenyl acetate, (i) ethyl benzoate, (j) acetamide, (k) butanamide, (l) potassium propanoate.
Problem 3
Explain the following observations. (a) The \(^{1} \mathrm{H}\) NMR spectrum of a solution of hexanoic acid contains a signal at \(\delta 11.2 \mathrm{ppm}\) but the signal disappears when \(\mathrm{D}_{2} \mathrm{O}\) is added to the solution. (b) The \(^{13} \mathrm{C}\) NMR spectrum of octanoic acid contains seven signals in the region \(\delta 14.1\) to \(34.3 \mathrm{ppm},\) and one signal at \(\delta 181.1 \mathrm{ppm}\) (c) The \(^{1}\) H NMR spectrum of butanone exhibits a triplet at \(\delta 1.06 \mathrm{ppm},\) a singlet at \(\delta 2.14 \mathrm{ppm}\) and a quartet at \(\delta 2.45 \mathrm{ppm}\) (d) The \(^{1} \mathrm{H}\) NMR spectrum of methyl formate shows signals at \(\delta 8.08\) and 3.77 ppm.
Problem 4
Comment on the following statements. (a) Keto-and enol-forms of a compound are isomers. (b) The equilibrium that describes the keto-enol tautomerism for butanone lies well over to the side of the keto-form. (c) Treatment of pentane- 2,4 -dione with base results in a monoanion.
Problem 8
Give methods of converting (a) \(o\) -bromotoluene into \(o\) -methylbenzoic acid, (b) toluene into benzoic acid and (c) 1-bromobutane into pentanoic acid.
Problem 10
(a) Suggest how each of the following Grignard reagents in \(\mathrm{Et}_{2} \mathrm{O}\) would react with solid \(\mathrm{CO}_{2}\) followed by treatment with \(\mathrm{H}^{+}\). (b) Give a mechanism for one of the reactions.
Problem 12
Outline how acetone reacts with \(\mathrm{I}_{2}\) in the presence of \((a)\) an acid catalyst and (b) a base catalyst. Give appropriate mechanisms for the reactions you describe.
Problem 13
Which of the following would undergo a haloform reaction when treated with \(\mathrm{Br}_{2}\) in the presence of NaOH: (a) pentan-3-one; (b) butanone; (c) propanone; (d) hexan-2-one; (e) hexan-3-one? Give the products in each case where you state the reaction will occur.
Problem 15
Elemental analysis for compound A gives \(71.9 \%\) C and \(12.1 \%\) H. In the mass spectrum of \(\mathbf{A}\) the parent ion comes at \(m / z=100\), and there is an intense fragmentation peak at \(m / z=43 .\) The IR spectrum of A has strong absorptions at \(2960-3000 \mathrm{cm}^{-1}\) and \(1718 \mathrm{cm}^{-1}\) as well as absorptions in the fingerprint region. In the \(^{13} \mathrm{C}\) NMR spectrum, there are signals at \(\delta 209.0,43.5\) 29.8,26.1,22.4 and 13.9 ppm. Compound \(\mathbf{A}\) can be reduced by \(\mathrm{NaBH}_{4},\) but is not oxidized by \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) in acidic solution. Suggest (with explanation \()\) the identity of \(\mathbf{A},\) and give the product of its reduction.
Problem 16
Give two synthetic methods by which carbon chains can be lengthened, illustrating your answer with reference to the conversion of 1-chloropentane to hexanoic acid.
Problem 22
Explain what is meant by the aldol reaction with reference to what happens when a small amount of \(\mathrm{NaOH}\) is added to (a) acetaldehyde and (b) acetone.
