Question 1

Which of the following pairs of molecules are constitutional isomers?

Accepted Answer

n-butane and isobutane

Question 2

What is the formal charge on the nitrogen atom in the ammonium ion ($$\mathrm{NH_4$^+}$$)?

Accepted Answer

$$+1$$

Question 3

Which of the following correctly represents a resonance structure for the acetate ion ($$\mathrm{CH_3COO^-}$$)?

Accepted Answer

One oxygen has a double bond to carbon, the other has a single bond and a negative charge; the positions of the double and single bonds can switch.

Question 4

What is the hybridization of the central carbon atom in formaldehyde ($$\mathrm{CH_2O}$$)?

Accepted Answer

$$sp^2$$

Question 5

Which of the following is the correct IUPAC name for the compound with the structure $$\mathrm{CH_3CH_2CH(CH_3$)CH_2CH_3}$$?

Accepted Answer

3-methylpentane

Question 6

Which of the following statements about cyclohexane conformations is TRUE?

Accepted Answer

The chair conformation is more stable than the boat conformation due to minimized torsional strain.

Question 7

Which of the following Newman projections represents the most stable conformation of ethane ($$\mathrm{C_2H_6}$$)?

Accepted Answer

Staggered conformation

Question 8

A molecule has the following structure: $$\mathrm{CH_3CHBrCH_2CH_3}. $$Which carbon is a chiral center?

Accepted Answer

The second carbon (the one bonded to Br)

Question 9

Assign the correct R/S configuration to the chiral center in (S)-2-butanol.

Accepted Answer

S

Question 10

Which of the following pairs are enantiomers?

Accepted Answer

(R)-2-butanol and (S)-2-butanol

Question 11

Which of the following functional groups is present in acetone?

Accepted Answer

Ketone

Question 12

Which of the following best explains why cyclopropane is less stable than cyclohexane?

Accepted Answer

Cyclopropane has significant angle strain and torsional strain due to its small ring size.

Question 13

Which of the following is the correct IUPAC name for the compound with the structure $$\mathrm{(CH_3$)_2CHCH_2CH_3}$$?

Accepted Answer

2-methylbutane

Question 14

Which of the following statements about stereoisomers is correct?

Accepted Answer

Enantiomers have identical physical properties except for the direction in which they rotate plane-polarized light.

Question 15

Which of the following best describes the electron-pushing arrows in resonance structures?

Accepted Answer

They show the movement of electrons, not atoms, between resonance forms.

Question 16

Which of the following is the most stable chair conformation of methylcyclohexane?

Accepted Answer

The conformation with the methyl group in the equatorial position

Question 17

A patient is given a medication that is a racemic mixture of two enantiomers. Which of the following is TRUE regarding the biological activity of the mixture?

Accepted Answer

The two enantiomers may have different biological activities in the body.

Question 18

Which of the following best describes the relationship between cis-1,2-dimethylcyclohexane and trans-1,2-dimethylcyclohexane?

Accepted Answer

They are diastereomers.

Question 19

Which of the following is the correct Lewis structure for the nitrate ion ($$\mathrm{NO_3$^-}$$)?

Accepted Answer

Nitrogen is bonded to three oxygens, with one double bond and two single bonds, and the negative charge is delocalized over the two singly bonded oxygens.

Question 20

Which of the following best explains why the anti conformation of butane is more stable than the gauche conformation?

Accepted Answer

In the anti conformation, the two methyl groups are as far apart as possible, minimizing steric hindrance.

Organic Chemistry Exam 1 Study Guide: Bonding, Alkanes, and Stereochemistry

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