Question 1

Which of the following statements best explains why alkenes have lower boiling points than alkanes of similar molecular weight?

Accepted Answer

Alkenes have weaker van der Waals interactions because the pi bonds prevent close packing.

Question 2

Calculate the index of hydrogen deficiency (IHD) for the compound with the formula $$\mathrm{C_6H_{10}}.$$

Accepted Answer

$$\mathrm{IHD} = 1$$

Question 3

Which of the following best describes the molecular orbital structure of ethylene ($$\mathrm{C_2H_4}$$)?

Accepted Answer

It has a sigma bond and a pi bond between the two carbons, with restricted rotation due to the pi bond.

Question 4

Which of the following alkenes exhibits cis-trans isomerism?

Accepted Answer

But-2-ene

Question 5

What is the correct IUPAC name for the following structure?

A six-carbon ring with a double bond and a methyl group at position 3.

Accepted Answer

3-methylcyclohexene

Question 6

Which of the following best describes Markovnikov’s rule in the addition of HBr to an asymmetric alkene?

Accepted Answer

The hydrogen atom adds to the carbon with the most hydrogens, and the bromine adds to the more substituted carbon.

Question 7

A chemist wants to synthesize a secondary alcohol from an alkene without carbocation rearrangement. Which reagent should they use?

Accepted Answer

$$\mathrm{Hg(OAc)_2}$$, $$\mathrm{H_2O}$$, then $$\mathrm{$$NaBH_4$$}$$

Question 8

Which of the following is true about the hydroboration-oxidation of alkenes?

Accepted Answer

It results in anti-Markovnikov addition and syn addition of H and OH.

Question 9

Which of the following best explains why tertiary carbocations are more stable than secondary or primary carbocations?

Accepted Answer

Tertiary carbocations have more hyperconjugation from neighboring sigma bonds.

Question 10

A student adds HBr to 1-butene in the presence of peroxides. What is the major product?

Accepted Answer

1-bromobutane (anti-Markovnikov addition)

Question 11

Which of the following is the correct IUPAC name for the compound shown below?

A five-carbon chain with a double bond between C1 and C2, a bromo group at C1, and a chloro group at C2.

Accepted Answer

1-bromo-2-chloropent-1-ene

Question 12

Which of the following best describes the stereochemistry of the product when Br$$_2 is $$added to cyclohexene?

Accepted Answer

A racemic mixture of enantiomers due to anti addition.

Question 13

Which of the following is NOT a possible reason for a carbocation rearrangement during an alkene hydration reaction?

Accepted Answer

To avoid forming a tertiary carbocation.

Question 14

Which of the following best describes the product of oxymercuration-reduction of 1-methylcyclopentene?

Accepted Answer

A racemic mixture of secondary alcohols at the more substituted carbon.

Question 15

Which of the following is the correct IUPAC name for a compound with a six-carbon chain, a double bond starting at C3, and a methyl group at C2?

Accepted Answer

2-methylhex-3-ene

Question 16

Which of the following best describes the difference between E/Z and cis/trans nomenclature for alkenes?

Accepted Answer

E/Z is based on the priority of substituents, while cis/trans is based on the relative position of identical groups.

Question 17

Which of the following best explains why hydroboration-oxidation of an alkene is stereospecific?

Accepted Answer

The boron and hydrogen add to the same side of the double bond (syn addition).

Question 18

A chemist needs to synthesize a primary alcohol from 1-hexene. Which sequence of reagents should they use?

Accepted Answer

$$\mathrm{BH_3$}$$, $$\mathrm{H_2O_2}$$, $$\mathrm{NaOH}$$

Question 19

Which of the following is the correct IUPAC name for a compound with a five-carbon ring, a double bond, and a chlorine at position 3?

Accepted Answer

3-chlorocyclopentene

Chapter 8: Alkenes I – Properties and Electrophilic Additions

Guida di studio - Domande di pratica