Question 1

Which statement best explains why geometric (cis/trans or E/Z) isomerism occurs in alkenes?

Accepted Answer

Alkenes have a double bond that restricts rotation, preventing the free movement of substituents around the bond.

Question 2

What is the bond dissociation energy of a carbon-carbon double bond ($$C=C) in $$alkenes, and how does it compare to a carbon-carbon single bond ($$C-C$$)?

Accepted Answer

The bond dissociation energy of $$C=C is $$approximately $$146$$ kcal/mol, which is higher than $$C-C$$ ($$83$$ kcal/mol).

Question 3

Given the molecular formula $$C_5H_8Br$$, what is the degree of unsaturation?

Accepted Answer

2

Question 4

Which of the following compounds has the highest degree of unsaturation?

Accepted Answer

$$CH_2=CH-CH$$=$$CH_2$$

Question 5

Which statement correctly describes the E/Z nomenclature for alkenes?

Accepted Answer

E isomer: higher priority groups are on opposite sides of the $$C=C$$ bond; Z isomer: higher priority groups are on the same side.

Question 6

Which of the following alkenes is the most stable according to alkyl substitution and heat of hydrogenation data?

Accepted Answer

Tetra-substituted alkene

Question 7

Why is the trans isomer of an alkene generally more stable than the cis isomer?

Accepted Answer

Trans isomers have less steric strain between substituents than cis isomers.

Question 8

Which of the following best describes the rate law for an E1 elimination reaction?

Accepted Answer

$$rate = k[	ext{substrate}]$$

Question 9

In an E2 elimination reaction, which condition is required for the reaction to proceed?

Accepted Answer

The hydrogen and the leaving group must be anti to each other.

Question 10

Which product will be favored in an E2 elimination reaction using sodium tert-butoxide ($$Na^+ - tBuO^-) as $$the base?

Accepted Answer

The least substituted alkene (Hofmann product)

Question 11

Which of the following statements about the dehydration of alcohols is correct?

Accepted Answer

It is catalyzed by a strong acid and usually follows Zaitsev's rule.

Question 12

Which of the following is a correct application of Zaitsev's Rule?

Accepted Answer

In elimination reactions, the most substituted alkene is usually the major product.

Question 13

Which of the following bases would most likely favor the formation of the Hofmann product in an E2 reaction?

Accepted Answer

Lithium diisopropylamide (LDA)

Question 14

Which of the following statements about the competition between $$S_N1/S_N2$$ and $$E1/E2$$ reactions is correct?

Accepted Answer

Good nucleophiles/strong bases favor $$S_N2/E2$$ reactions.

Question 15

A compound has the molecular formula $$C_7H_{10}O. $$What is its degree of unsaturation?

Accepted Answer

4

Question 16

Which of the following is NOT a requirement for the E2 mechanism to occur?

Accepted Answer

The leaving group and the hydrogen must be syn to each other.

Question 17

Which of the following statements about bond length in alkenes is correct?

Accepted Answer

The $$C=C$$ bond length is shorter than the $$C-C$$ bond length.

Question 18

Which of the following is true regarding the formation of alkenes via elimination reactions?

Accepted Answer

Elimination reactions result in the formation of a new $$\pi$$ bond.

Question 19

Which of the following statements about the E1 and E2 mechanisms is correct?

Accepted Answer

E1 is unimolecular and E2 is bimolecular with respect to the rate-determining step.

Structure and Synthesis of Alkenes: Elimination (Chapter 7 Study Notes)

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