Question 1

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

Accepted Answer

$$\mathrm{C}_n\mathrm{H}_{2n+2}$$

Question 2

Which of the following statements best describes constitutional isomers?

Accepted Answer

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

Question 3

What is the IUPAC name for the following structure: $$\mathrm{CH}_3\mathrm{CH}_2\mathrm{CH}_2\mathrm{CH}_3$$?

Accepted Answer

Butane

Question 4

Which of the following is the correct IUPAC name for a molecule with the structure $$\mathrm{CH}_3\mathrm{CH}(	ext{CH}_3)\mathrm{CH}_2\mathrm{CH}_3$$?

Accepted Answer

2-methylbutane

Question 5

Which conformation of ethane is the most stable and why?

Accepted Answer

Staggered, because the C-H bonds are as far apart as possible, minimizing electron repulsion.

Question 6

What is the dihedral angle between adjacent C-H bonds in the staggered conformation of ethane?

Accepted Answer

$$60^\circ$$

Question 7

Which of the following best explains why branching in alkanes lowers their boiling point?

Accepted Answer

Branching decreases the surface area, leading to weaker London dispersion forces.

Question 8

A compound has the molecular formula $$\mathrm{C}_5\mathrm{H}_{12}. $$How many constitutional isomers are possible for this compound?

Accepted Answer

3

Question 9

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

$$\mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}_2-\mathrm{CH}_3$$

Accepted Answer

2-methylpentane

Question 10

Which of the following is NOT a type of strain found in cyclobutane?

Accepted Answer

Pi bond strain

Question 11

What is the main reason the chair conformation of cyclohexane is more stable than the boat conformation?

Accepted Answer

The chair conformation has less torsional and steric strain.

Question 12

Which of the following best describes the effect of a tert-butyl group on the chair conformation of cyclohexane?

Accepted Answer

It must be in the equatorial position to minimize steric strain.

Question 13

Which of the following is the correct balanced equation for the complete combustion of methane?

Accepted Answer

$$\mathrm{CH}_4 + 2\mathrm{O}_2 \rightarrow \mathrm{CO}_2 + 2\mathrm{H}_2\mathrm{O}$$

Question 14

Which of the following is true about the physical properties of alkanes?

Accepted Answer

Alkanes are insoluble in water and have lower boiling points than more polar compounds of similar molecular weight.

Question 15

Which of the following best describes the relationship between oxidation and reduction in organic chemistry?

Accepted Answer

Oxidation is an increase in C-O bonds or a decrease in C-H bonds; reduction is a decrease in C-O bonds or an increase in C-H bonds.

Question 16

Which of the following is the correct IUPAC name for a molecule with two methyl groups on the second and third carbons of pentane?

Accepted Answer

2,3-dimethylpentane

Question 17

Which of the following is a correct statement about the naming of cycloalkanes with two different substituents?

Accepted Answer

Number the ring to assign the lower number to the substituent that comes first alphabetically.

Question 18

Which of the following best describes a Newman projection?

Accepted Answer

A way to represent the 3D arrangement of atoms by looking down a bond axis.

Question 19

Which of the following is the correct order of increasing stability for the conformations of butane?

Accepted Answer

Eclipsed \u003c Gauche \u003c Anti

Alkanes: Structure, Nomenclature, Isomerism, and Conformations

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