Question 1

Which of the following statements best describes a constitutional isomer?

Accepted Answer

Compounds with the same molecular formula but different connectivity of atoms.

Question 2

What is the hybridization and approximate bond angle around each carbon atom in ethane ($$\mathrm{C_2H_6}$$)?

Accepted Answer

sp$$^3$$ hybridization; bond angle $$\approx 109.5^\circ$$

Question 3

Which of the following is the correct IUPAC name for the compound with the structure $$\mathrm{CH_3CH(CH_3$)CH_2CH_3}$$?

Accepted Answer

2-methylbutane

Question 4

Which of the following best describes the difference between a staggered and an eclipsed conformation of ethane?

Accepted Answer

In the staggered conformation, the hydrogen atoms on adjacent carbons are as far apart as possible, minimizing torsional strain.

Question 5

Which of the following is NOT a correct statement about cyclohexane conformations?

Accepted Answer

The boat conformation is more stable than the chair conformation.

Question 6

Given the following reaction: $$\mathrm{C_6H_{12} + 1.5\ O_2$ \rightarrow 6\ CO_2$ + 6\ H_2O}$$, which compound would release the most heat per $$\mathrm{CH_2$}$$ group upon combustion?

Accepted Answer

Cyclopropane

Question 7

Which of the following best explains why cyclopropane is more reactive than cyclohexane?

Accepted Answer

Cyclopropane has significant ring strain due to its bond angles being much less than $$109.5^\circ.$$

Question 8

Which of the following is the correct order of increasing ring strain for the following cycloalkanes: cyclohexane, cyclopentane, cyclobutane, cyclopropane?

Accepted Answer

Cyclohexane \u003c cyclopentane \u003c cyclobutane \u003c cyclopropane

Question 9

Which of the following is a correct statement about constitutional isomers?

Accepted Answer

They have the same molecular formula but different connectivity of atoms.

Question 10

A hydrocarbon with the formula $$\mathrm{C_5H_{10}}$$ could be which of the following?

Accepted Answer

A cycloalkane or an alkene

Question 11

Which of the following best describes the difference between a primary (1°) and a tertiary (3°) carbon atom?

Accepted Answer

A primary carbon is attached to one other carbon, while a tertiary carbon is attached to three other carbons.

Question 12

Which of the following is the correct general formula for an alkane?

Accepted Answer

$$\mathrm{C_nH_{2n+2}}$$

Question 13

Which of the following best describes the relationship between $$K_{eq}$$ and $$\Delta G^\circ$$ for a conformational equilibrium?

Accepted Answer

$$\Delta G^\circ = -2.3RT \log K_{eq}$$

Question 14

Which of the following is true about the energy barrier for rotation about the C–C bond in ethane?

Accepted Answer

It is due to torsional strain and is approximately 3.0 kcal/mol.

Question 15

Which of the following best describes a gauche interaction in butane?

Accepted Answer

A conformation where two methyl groups are $$60^\circ$$ apart, leading to increased steric strain.

Question 16

Which of the following is true about cis/trans isomerism in cycloalkanes?

Accepted Answer

Cis isomers have substituents on the same face of the ring, while trans isomers have them on opposite faces.

Question 17

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

$$\mathrm{CH_3CH_2CH(CH_3$)CH_2CH_3}$$

Accepted Answer

3-methylpentane

Question 18

Which of the following statements about aromatic hydrocarbons is correct?

Accepted Answer

They contain rings with alternating single and double C–C bonds.

Question 19

A student draws two structures for $$\mathrm{C_4H_{10}}$$ and finds that they cannot be interconverted by rotation about single bonds. What is the relationship between these two structures?

Accepted Answer

They are constitutional isomers.

Hydrocarbons: Nomenclature, Isomerism, and Conformational Analysis

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