Elimination Reactions
1. Predict the major product in the following reaction?
CH3
Cl
CH3
H2O
CH3
CH3
OH
CH3
CH3
OH
H
a.
H
CH3
HO
CH3
b.
c.
d. none
2. Arrange the following alkyl bromides in the increasing order of reaction rate towards nucleophilic
substitution with iodide in acetone at 50 degrees?
(i) Allyl bromide
ii. Propyl bromide
a. i< ii<iii<iv
b. ii=iv<iii<iv
iii. Benzyl bromide
iv. Isopropyl bromide
c. ii=iv<iii=iv
d. ii=iv<i<iii
3. What is the major product obtained in the following reaction?
Br
H
H
Ph
Ph
NaOEt/EtOH, Heat
CH3
a. cis- 1,2-diphenylpropene
b. trans- 1,2-diphenylpropene
c. 2,3-diphenylpropanol
d. a&b
4. Which alkyl halide and what condition must be used to prepare methylenecyclohexane in good
yield by E2 elimination?
a. 1-Bromo-1-methylcyclohaxane + NaOEt/EtOH
b. 1-Bromo-1-methylcyclohaxane + Na(terBuO)/ terBuOH
c.
Cyclohexylbromomethane + NaOEt/EtOH
d. Cyclohexylbromomethane + Na(terBuO)/ terBuOH
5. Which of the following will have the highest ratio of E2 to SN2 products expected in their
reactions with sodium ethoxide in ethyl alcohol?
a. methyl iodide
b. isobutyl bromide
c.
1-bromo-4,4-dimethylbutane
d.
2-bromo-3-methylbutane
6. Which of the following statements about E2 reaction is false?
a. E2 reactions normally occur with anti stereochemistry.
b. E2 reactions show substantial primary deuterium isotope effect.
c.
E2 reactions are favoured by alkyl branches at alpha- and beta-carbons in alkyl halides,
by alkyl branches in the base and by stronger bases.
d. None of the above.
7. Which of the following statements is/ are wrong?
a. Tertiary alkyl halides are more reactive towards solvolysis reactions by SN1 and E1
mechanisms.
b. E1 and SN1 reactions are accelerated polar aprotic solvents.
c.
1
The best leaving groups give the weakest bases as products.
Elimination Reactions/ AIJ/SJC/TRY-2/28-02-2010
d. Rearranged carbocations lead to form racemic products in eliminations mechanisms.
8. Predict the product:
2-bromo-3-methylbutane
anhydrous acetone
a. 2-methlbut-2-ene
b. 3-methylbutene
c. 3-methyl-2-butanol
d. no reaction
9. Which of the following is/ are true about the following observation?
Neo-pentylbromide + excess NaOC2H5 / C2H5OH
NO REACTION
i)
As there are no beta-hydrogens, no elimination is possible.
ii)
Neopentyl halides are essentially unreactive in S N2 reactions.
iii) Because primary alkyl halides do not form carbocations, neither SN1 nor E1 is possible.
iv) If the reaction mixture were heated strongly, some SN2 reactions might occur in a few
days.
a. I, ii & iv
b. ii & iv c. all
d. none
10. Match the following heats of hydrogenation (kcal) with the alkenes given.
i.
cis-2-butene
p. 30.3
ii.
trans-2-butene
q. 26.9
iii. isobutylene r. 27.6
iv. isopentylene
s. 28.9
a. i-r; ii-q; iii-p; iv-s
b. i-q; ii-r;I ii-s; iv-p
c. i-s; ii-r; iii-q; iv-p
d. i-r; ii-s; iii-q; iv-p
11. What is the major product when E2 elimination converts the diastereo menthyl chloride?
a. 2-menthene
b. 3-menthene
c. 50 % a & b
d. none
12. Which of the following is fast debrominated?
Br
Br
Br
Br
b
a
d
c
13. Which of the following has the highest rate of elimination with sodium ethoxide in ethanol at 55
degrees?(MB,302)
a. Ethyl bromide
b. Propyl bromide
c. Isopropyl bromide
d. Tertiarybutyl bromide
14. Which of the following is the major product when 3-methyl-2-butyltosylate undergoes elimination
in n-butanol?(MB 305)
a. 2-methyl-2-butene
b. 3-methl-1-butene
butene
15. Fsdgs
16. Dfgsdgsdfgsad
2
Elimination Reactions/ AIJ/SJC/TRY-2/28-02-2010
c. 2-methyl-1-butene
d. 2,3-dimethyl-2-
17. gf
3
Elimination Reactions/ AIJ/SJC/TRY-2/28-02-2010