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Columbia University C99ORG22ak.DOC Chem S3444Q Summer 99 Professor Irving J. Borowitz Exam No. 2 Answer Key July 28, 1999
Name: Grade: Please use a non-red pen. Answer questions in the provided space. If you write any answers on the back of the page, indicate this on the front of that page. Points appear in parentheses ( ) and margin. Good Luck! Question Max. Pts. Pts Question Max. Pts Points
- 5 + 5 + 5 = 15 4. 4 + 6 + 6 = 16
- 4 + 6 + 4 + 4 + 4 = 22 5. ( 3 + 3 ) + 3 +3+3 = 15
- 3 + ( 2 + 2 + 2 ) + ( 2 + 2 ) = 13 6. 4 + 3 + 4 + 4 + 2+2 = 19
Total = 100
- (15 ) Write a detailed mechanism for each of the following reactions. Use arrows to show electron flow.
a. (CH 3 ) 2 C=O + CH 2 PPh 3 dimethoxy ethane^ (CH 3 ) 2 C=CH 2 + Ph 3 P=O
GRADERS: Accept loss of 0=PPh 3 from either open dipolar or closed 4-membered ring forms
C (^) H
O CH 3 CH 2 -C-H
O NaOH, H 2 O added slowl y
H 3 O H 2 O
H 2 O
Ph HC== C
CH 3 CH=O
b.
c. PhCH=O + NH 2 - NH-Ph + H+^ →→ PhCH=N-NHPh + H 2 O
Accept protonation either before or after carbonyl addition
- (22) Fill in the missing reagents, or products A-I for the following reaction sequences. Sometimes more than one step is needed for individual conversions.
Ph-C=O H
Ph C Cl O
a.?^? S
H S
Ph Li+^ --HAl(OtBu) 3 HSCH 2 CH 2 SH/ H+ or H 2 / Pd- poisoned catalyst or BF 3 (Lindlar’s catalyst)
CH 3 CH 2 CH 2 C OH
O 1.?
2.? CH^3 CH^2 CH^2 C^ CH^3
O b. H- C^ N? H ANS= 1. SOCl 2 or PCl 3
- (CH 3 ) 2 CuLi or (CH 3 ) 2 Cd
c. (^) CH 3 CH Ph
OH?^ CH 3 C Ph
O Ph-C-O-OH
O
?
d. Circle which molecule below reacts FASTER and give the product(s) of that reaction
N
O
H
or CH 3
O
NH CH 3 OH, H^2 O
?
This ring is FASTER
4pt
e. Briefly explain the FASTER rate in 2d.
The β-lactam (4-membered cyclic amide) reacts FASTER since it has ring strain which is relieved upon opening
4pt
O C
O
CH 2 CH 2 NH 2
- (16) a. Rank the following compounds in order of decreasing acidity (strongest = 1 to weakest = 5).
C
O O H
CH (^3)
C
O O H
NO (^2)
C
O O H
CH 3 C
O CH 3 CH 2 O H O H
(1) (2) (3) (4) (5)
Ranking: 3 5 1 4 2
b. Distinguish between the members of each of the following pairs of compounds by the requested number of chemical tests or reactions. Write the equations and the structures of all the major organic and inorganic products. Note the observations for the tests.
6pt
( 1 ) (^) Use one test or reaction with equation and visible result and one specific IR or 1H-NMR fact to distinguish.
Ph C
O CH 2 CH (^3) PhCH 2 CH 2 C
O H
CrO 3 : no color change CrO 3 (or KMnO 4 , Tollens, etc.)) → PhCH 2 CH 2 CO 2 H + Cr+
If a test: orange solution → green
Or NaBH 4 : reduction to 2O^ alcohol reduction to a 1o^ alcohol (very slow rxn with ZnCl 2 / HCl) (then a moderate rxn with ZnCl 2 /HCl →R-Cl) IR PhC=O 1690 cm-1^ RCH=O 1725 cm- Extra CH stretch ~ NMR δ 1.2 CH 3 (t,3); 2.5 CH 2 (quart,2) no quartet; δ 9.5 O=CH (s,1); Ph 7.1 (s,5); PhCH 2 (t,2) Ph: 2 mult 7-8 (ortho downfield) CH 2 CH=O ( ca 2.2-2.4 (sextet, 2) Not a singlet; no sextet
Use one test or reaction with equation and visible result and ( 2 ) any two specific IR or 1H-NMR facts to distinguish.
Ph CH 2 C^ Cl
O CH 2 CH CH 2 C
O CH 3
6pt a, no reaction a. H 2 O: gives PhCH 2 CO 2 H + HCl
b. Br 2 decolorizes if a test); if rxn: adds to double b. no color change (maybe slow reaction → bond PhCH 2 C(=O)Br + BrCl c. NaOI/ NaOH gives CHI 3 (yellow ppt) no yellow ppt ( rxn gives PhCH 2 CO 2 Na) d. 2,4-DNPH gives a yellow ppt R-C(CH 3 )=NNHC 6 H 3 (NO 2 ) 2 no rxn e. R-NH 2 : no rxn RNH2: converts the acid chloride to an amide PhCH 2 C(=O)NHR f. Ag+^ no rxn Ag+^ gives AgCl white ppt (rxn or test) IR: C=O 1715 cm-1^ ; no aromatic peaks 600-800 C=O 1800; 2 peaks 600- C=C ~1620 – 1650 aromatic C=C 1600 NMR δ 2.1 (s,3), vinyl Hs 5-6 no δ 5-6, no 2.1 but instead phenyl at 7.1 (s,5)
(15) a. Write the structures of the reactant(s) that are used to make each of the following polymers: Note that more than one reactant may or may not be necessary.
n
N (CH 2 ) 5 C N
H O^ H (CH 2 ) 5 C
O ( 1 )?
3 n
( 2 ) C
O C
O O CH 2 CH 2 O
b. Accurately name the above polymers.
(1) Nylon-6 (-0.5 pt for Nylon-66)
3Pt (1.5 pt x 2)
(2) poly (ethylene terphthalate); Dacron , polyester
c. In the acid catalyzed hydrolysis of PhCOCH^3
O
with H 218 O where is the 18 O isotopic label found in the products? Explain by giving the mechanism and the products of the reaction. 3pt
The 18 Oxygen is found in both the OH and the carbonyl group of the benzoic acid (PhCO 2 H) product:
c. Which of the following statement(s) concerning nitriles (R-C↵N) is incorrect? 3pt
- nitriles can be hydrolyzed to carboxylic acids
- nitriles can be formed from (many) alkyl halides by nucleophilic substitution by cyanide ion
- nitriles can be reduced with excess LiAlH 4 to primary amines RNH 2
- nitriles react with RMgX (Grignard reagents) to form tertiary alcohols (incorrect ans.)**
- nitriles can be made by dehydration of amides
