1559T_ch20_358-37211/09/0518:53Pa9e365 EQA Solutions to Problems.365 42.Amide the following options: CON(CH-CH32 Method 1:Direct reaction between an amine and an acid first gives a salt:strong heating converts the salt sofsof water Method :Converts to alkanoyl chloridectnh The starting cyclic amide(a lactam)p we can proce ⊕ 0-CH,2-0 -0-CH OCH (See Problem40) 14.CH COCH3:NH CH CH 0 CH;C COCH CH;C NH2 +CH,OH NH. inCH.CH.CH.CH.CH-NCH acid.(e) a)and (f).whe ntanal:N.N-dimethylpentanamide Solutions to Problems • 365 42. Amides may be made directly from the acids, or indirectly via alkanoyl halides, anhydrides (less efficiently, because only one of the two alkanoyl groups is converted into an amide), or esters. Thus we have the following options: Method 1: Direct reaction between an amine and an acid first gives a salt; strong heating converts the salt to the amide with loss of water. Method 2: Converts to alkanoyl chloride; reaction with amine gives amide with loss of HCl. Often done in the presence of excess amine to consume the HCl. Method 3: Esterification with any inexpensive alcohol (ethanol chosen here), then reaction with the amine under mild heating. 43. Dimethyl sulfate is a highly reactive SN2 substrate with respect to attack by a nucleophile on a methyl group (similar to CH3I in reactivity). The process displaces the methyl sulfate anion, a good leaving group. The starting cyclic amide (a lactam) possesses two possible nucleophilic atoms, nitrogen and oxygen. Reac￾tion of the oxygen with an electrophile gives a resonance-stabilized intermediate; reaction of the nitrogen does not. Therefore, we can proceed as follows: 44. 45. Pentanamide gives (a) pentanoic acid, (e) pentanamine, and (f) pentanal; N,N-dimethylpentanamide gives the same products for (a) and (f), whereas LiAlH4 reduction in this case gives N,N-dimethylpentanamine, CH3CH2CH2CH2CH2N(CH3)2. OCH3 CH3CNH2 CH3OH H O NH2 CH3C O CH3COCH3 OCH3 O NH3 NH3 CH3C O (See Problem 40) OCH3 H N OCH3 N OCH3 H N H N H O O O H3C O S CH O 3 SN2 O O O S CH O 3 CO2H 1. (CH3CH2)2NH 2. strong heating 1. CH3CH2OH, H 2. (CH3CH2)2NH,  1. SOCl2 2. (CH3CH2)2NH H3C CON(CH2CH3)2 H3C 1559T_ch20_358-372 11/09/05 18:53 Page 365