Question 1

Which of the following statements best describes a Lewis acid?

Accepted Answer

A substance that accepts a pair of electrons to form a new covalent bond.

Question 2

Consider the following acid-base reaction in aqueous solution:

$$\mathrm{CH_3COOH + NH_3$ \rightleftharpoons CH_3COO^- + NH_4$^+}$$

Which direction will the equilibrium favor, and why?

Accepted Answer

To the right, because $$\mathrm{CH_3COOH} is a $$stronger acid than $$\mathrm{NH_4$^+}.$$

Question 3

Which of the following factors would most increase the acidity of a molecule according to the ARIO (Atom, Resonance, Inductive, Orbital) effects?

Accepted Answer

Delocalizing the negative charge through resonance.

Question 4

Which solvent would best stabilize the conjugate base of phenol ($$\mathrm{C_6H_5OH}) $$and thus increase its acidity?

Accepted Answer

Water (polar protic solvent)

Question 5

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

$$\mathrm{CH_3CH_2CH_2CH_2CH_3}$$

Accepted Answer

n-Pentane

Question 6

Which of the following Newman projections represents the most stable conformation of butane ($$\mathrm{C_4H_{10}}) $$when viewed along the C2–C3 bond?

Accepted Answer

Anti conformation with methyl groups $$180^\circ$$ apart.

Question 7

A cyclohexane ring has a single methyl group attached. Which conformation is more stable and why?

Accepted Answer

Equatorial, because it minimizes steric strain.

Question 8

Which of the following pairs are constitutional isomers?

Accepted Answer

n-Butane and isobutane

Question 9

How many stereoisomers are possible for 2,3-dibromobutane?

Accepted Answer

4

Question 10

Which of the following compounds is chiral?

Accepted Answer

2-Butanol

Question 11

Assign the correct configuration (R or S) to the chiral center in (R)-2-bromobutane.

Accepted Answer

The configuration is R.

Question 12

Which of the following statements about meso compounds is correct?

Accepted Answer

Meso compounds are achiral despite having chiral centers.

Question 13

Which of the following alkenes is assigned the E configuration?

Accepted Answer

An alkene where the two highest priority groups are on opposite sides.

Question 14

A solution of (S)-2-butanol rotates plane-polarized light to the left. What can you conclude about its optical activity?

Accepted Answer

(S)-2-butanol is optically active and levorotatory.

Question 15

Which of the following best explains why the conjugate base of acetic acid ($$\mathrm{CH_3COO^-}) is $$stabilized?

Accepted Answer

The negative charge is delocalized by resonance over two oxygen atoms.

Question 16

Which of the following best describes the relationship between (R)-2-butanol and (S)-2-butanol?

Accepted Answer

They are enantiomers.

Question 17

Which of the following statements about the free rotation around a C–C single bond is correct?

Accepted Answer

Eclipsed conformations are higher in energy than staggered conformations.

Question 18

Which of the following best describes the difference between cis and trans isomers in cycloalkanes?

Accepted Answer

Trans isomers have substituents on opposite sides of the ring.

Question 19

Which of the following statements is true regarding the number of stereoisomers for a molecule with $$n$$ chiral centers and no plane of symmetry?

Accepted Answer

The maximum number of stereoisomers is $$2^n.$$

Question 20

Which of the following best explains why tert-butanol ($$\mathrm{(CH_3$)_3COH}) is $$less acidic than ethanol ($$\mathrm{CH_3CH_2OH}$$)?

Accepted Answer

The conjugate base of tert-butanol is destabilized by electron-donating alkyl groups.

Organic Chemistry Study Guide: Acids and Bases, Alkanes & Cycloalkanes, Stereochemistry (Chapters 3-5)

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