20.2 Outline a procedure for separating a mixture

20.36 A commercial synthesis of folic acid consists of heating the following three compounds with
aqueous sodium bicarbonate. Propose reasonable mechanisms for the reactions that lead to folic
acid.
Answers:
H 2N
H 2N
N
N
N
OH
H2N
N
OH
N
NH 2
NH 2
N
N
+
N
OH
Br
O
NH2
NH2
Br
Br
+
O
CHBr 2CCH 2Br
H 2N
COOH
+ H 2N CONHCHCH 2CH 2COOH
HCO 3,H 2O
Folic acid (~10%)
N
N
OH
NH 2
H
N CONHCHCH 2CH 2COOH
COOH
20.37 When compound W(C15H17N) is treated with benzenesulfonyl chloride and aqueous
potassium hydroxide, no apparent change occurs. Acidification of this mixture gives a clear
solution. The 1 H NMR spectrum of W is shown in Fig.20.7. Propose a structure for W.
Answer:
N
N-benzyl-N-ethylaniline
20.38 Propose structures for compounds X, Y, and Z.
X(C 7H 7Br) NaCN
Y(C 8H 7N) LiAlH 4
Z(C 8H 11N)
The 1 H NMR spectrum of X gives two signals, a multiplet at δ7.3(5H) and a singlet at δ
4.25(2H); the 680-840-cm -1 region of the IR spectrum of Y is similar to that of X: multiplet at δ
7.3(5H), singlet at δ3.7(2H). The 1 H NMR spectrum of Z is shown in Fig.20.8.
Answer:
X
Br
; Y
CN
; Z
N
Br
Br
Br
NH 2
H 2N
.
H 2N
N
N
N
OH
N
OH
H
N
N
N
N
HCO 3 -
Br
Br
Br