Question 1

Which statement best explains why trans alkenes are generally more stable than cis alkenes?

Accepted Answer

Trans alkenes have less steric hindrance between substituents on opposite sides of the double bond.

Question 2

According to Zaitsev's Rule, which product will be favored in the E2 elimination of 2-bromo-2-methylbutane with sodium ethoxide?

Accepted Answer

The most highly substituted alkene, 2-methyl-2-butene.

Question 3

Which base would you use to favor the formation of the least substituted alkene in an E2 elimination reaction?

Accepted Answer

Potassium tert-butoxide $$((CH_3$)_3CO^-K^+)$$

Question 4

Which of the following statements about the E2 mechanism is correct?

Accepted Answer

All four atoms involved in the elimination must be coplanar in the transition state.

Question 5

What is the major product when 2-bromo-2-methylbutane is treated with potassium tert-butoxide?

Accepted Answer

2-methyl-1-butene (the least substituted alkene)

Question 6

Which of the following best describes the transition state of an E2 elimination reaction?

Accepted Answer

It has partial double bond character between the two carbons involved.

Question 7

Why are tertiary alcohols dehydrated more easily than primary alcohols under acidic conditions?

Accepted Answer

Tertiary carbocations formed during dehydration are more stable due to greater alkyl substitution.

Question 8

Which of the following is true regarding the dehydration of primary alcohols?

Accepted Answer

Primary alcohols typically undergo E2 elimination because the carbocation intermediate is too unstable for E1.

Question 9

A hydride shift during the dehydration of a secondary alcohol results in:

Accepted Answer

Formation of a more stable carbocation intermediate.

Question 10

Which of the following statements about the acidity of terminal alkynes is correct?

Accepted Answer

Terminal alkynes have a pKa around 25, making them more acidic than alkanes and alkenes.

Question 11

Which reagent is commonly used to convert a vicinal dihalide to an alkyne?

Accepted Answer

Excess sodium amide $$($$NaNH_2$$)$$

Question 12

What is the role of a metal catalyst in the hydrogenation of alkenes?

Accepted Answer

It provides a lower energy pathway for the reaction, decreasing the activation energy $$(\Delta G^*).$$

Question 13

Which product is formed when 1-hexyne is partially hydrogenated using Lindlar's catalyst?

Accepted Answer

cis-2-hexene

Question 14

In the E2 elimination of cyclohexyl chloride, which conformation is required for the reaction to proceed?

Accepted Answer

The leaving group and the hydrogen to be eliminated must both be axial (anti-coplanar).

Question 15

Which of the following statements about the use of sodium alkynides in organic synthesis is correct?

Accepted Answer

Sodium alkynides can act as nucleophiles in $$S_N2$$ reactions to form new carbon-carbon bonds.

Question 16

Which of the following is the correct order of alkene stability from least to most stable?

Accepted Answer

Unsubstituted \u003c Monosubstituted \u003c Disubstituted \u003c Trisubstituted \u003c Tetrasubstituted

Question 17

Which of the following best describes syn addition in the hydrogenation of alkenes?

Accepted Answer

Both hydrogen atoms add to the same face of the double bond.

Question 18

Which catalyst is used for the selective hydrogenation of alkynes to cis-alkenes?

Accepted Answer

Lindlar's catalyst (NiB or Pd/CaCO$$_3$$ with quinoline)

Question 19

Which of the following statements about the Cahn-Ingold-Prelog (E)-(Z) system is correct?

Accepted Answer

The (Z) isomer has the highest priority groups on the same side of the double bond.

Question 20

Which of the following is a consequence of carbocation rearrangement during alcohol dehydration?

Accepted Answer

A more substituted alkene may be formed due to increased carbocation stability.

Alkenes and Alkynes I: Properties and Synthesis – Elimination Reactions of Alkyl Halides

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