20_all_ - 20.1 Outline a procedure for separating...

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20.1 Outline a procedure for separating hexylamine from cyclohexane using dilute HCl, aqueous NaOH, and diethyl ether. Answer: CH 3 (CH 2 ) 5 NH 2 dil HCl ether organic phase: aqueous phase dry distill NaOH ether dry distill CH 3 (CH 2 ) 5 NH 2 organic phase 20.2 Outline a procedure for separating a mixture of benzoic acid, p-cresol, aniline and benzene using acids, bases, and organic solvents. Answer: dil HCl ether organic phase: aqueous phase dry distill NaOH ether dry distill NaOH,H 2 O ether COOH OH NH 2 NH 2 aqueous phase organic phase mixtures OH recrystallization COOH organic phase NaHCO 3 ether organic phase: aqueous phase dry distill HCl 20.3 (a) Write resonance structure for the phthalimide anion that account for the acidity of phthalimide. (b) Would you expect phthalimide to be more or less acidic than benzamide? Why? (c) After step 2 of our reaction, several steps have been omitted. Propose reasonable mechanisms for these steps. Answer : (a) O O N O O N (b) More acidic than benzamide . Because there are two C=O (carbonyl groups) attached to the N which is a electric withdrawing group, so that the ccarbonyl group can stabilize the N anion. In this case, phthalimide is much easier to release hydrogen, which means it is more acidic.
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(c) O O NR H 2 NN H 2 O O H H 2 H O O N H R N H NH 2 O OH NH NH O O H 2 NH NH + H 20.4 Outline a preparation of benzylamine using the Gabriel synthesis. O O N H KOH O O N K X O O N H 2 H 2 OH O H N N H NH 2 ethanol several steps O O N H N H + H 2 N 20.5 Show how you might prepare each of the following amines through reductive amination: a) CH 3 (CH 2 ) 3 CH 2 NH 2 NH 2 O H NH 3 ,H 2 ,Ni b) C 6 H 5 CH 2 CH(NH 2 )CH 3 NH 2 O NH 3 ,H 2 ,Ni c) CH 3 (CH 2 ) 4 CH 2 NHC 6 H 5 N H O H NH 2 H 2 ,Ni d) C 6 H 5 CH 2 N(CH 3 ) 2
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N O H N H H 2 ,Ni 20.6 Reductive amination of a ketone is almost always a better method for the preparation of amines of the type RCH(R’)NH 2 than treatment of an alkyl halide with ammonia. Why would this be true? Answer: I think the reasons are: 1) The multiple alkylations occurs when alkyl halide reacts with ammonium, so the method is of very limited synthetic application. 2) I found that if it is treated by ketone, the possible way is only one, so this reaction can be controlled well. Above all, we can reach the conclusion easily that reductive amination of a ketone is almost always a better method for the preparation of amines. 20.7 Show how you might utilize the reduction of an amide, oxime, or nitrile to carry out each of the following transformations: (a) Benzoic acid to benzylethylamine (b) 1-Bromopentane to hexylamine (c) Propanoic acid to tripropylamine (d) Butanone to sec-butylamine Answer: (a) COOH COCl C OHN (1) LiALH 4 ,Et 2 O (2) H 2 O H N SOCl 2 NH 2 C 2 H 5 (1) LiALH 4 ,Et 2 O (2) H 2 O (b) NaCN CH 2 Br(CH 2 ) 3 3 2 CN(CH 2 ) 3 CH 3 NH 2 (CH 2 ) 5 CH 3 (c) CH 3 CH 2 COOH Cl O (1) LiALH 4 ,Et 2 O (2) H 2 O SOCl 2 NH(CH 2 CH 2 CH 3 ) 2 O N(CH 2 CH 2 CH 3 ) 2 (CH 3 CH 2 CH 2 ) 3 N (d) O NH3 NH 2 LiBH 3 CN
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20.8 Using a different method for each part, but taking care in each case to select a good method,
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This note was uploaded on 02/23/2010 for the course CHEM 101 taught by Professor Smith during the Spring '10 term at Duke.

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20_all_ - 20.1 Outline a procedure for separating...

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