Question 1

Which of the following statements best describes the difference between Lewis structures and line-angle (stick) structures for organic molecules?

Accepted Answer

Lewis structures show all atoms and bonds, including lone pairs, while line-angle structures omit carbon and hydrogen atoms bonded to carbon, representing bonds as lines.

Question 2

Given the molecule ethanol ($$\mathrm{CH_3CH_2OH}$$), which type of intermolecular force is most significant in determining its boiling point?

Accepted Answer

Hydrogen bonding

Question 3

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

$$\mathrm{CH_3CH_2CH_2CH_2CH_3}$$

Accepted Answer

Pentane

Question 4

A cyclohexane molecule can adopt different chair conformations. If a methyl group is placed on carbon 1 and a bromine on carbon 2, which conformation is more stable?

Accepted Answer

The conformation where both substituents are equatorial

Question 5

Which of the following statements about resonance structures is correct?

Accepted Answer

Resonance structures represent delocalization of electrons and the true structure is a hybrid of all possible resonance forms.

Question 6

Rank the following compounds in order of increasing acidity (lowest to highest): $$\mathrm{CH_4$}$$, $$\mathrm{CH_3OH}$$, $$\mathrm{CH_3COOH}.$$

Accepted Answer

$$\mathrm{CH_4$} \u003c \mathrm{CH_3OH} \u003c \mathrm{CH_3COOH}$$

Question 7

Which of the following is a correct statement about the SN2 reaction mechanism?

Accepted Answer

The reaction rate depends on both the concentration of the nucleophile and the substrate.

Question 8

A student is asked to predict the major product of the following reaction:

$$\mathrm{2{-}methylpropane + Cl_2$ \xrightarrow{hv} ?}$$

Which is the major product?

Accepted Answer

$$\mathrm{2{-}chloro{-}2{-}methylpropane}$$

Question 9

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

Accepted Answer

Tertiary carbocations are stabilized by hyperconjugation and inductive effects from three alkyl groups.

Question 10

Which of the following is the correct product for the acid-catalyzed hydration of 2-methyl-2-butene ($$\mathrm{CH_3C(CH_3$)=$$CHCH_3$$}) $$with water?

Accepted Answer

$$\mathrm{2{-}methyl{-}2{-}butanol}$$

Question 11

Which of the following statements about stereoisomers is correct?

Accepted Answer

Enantiomers are non-superimposable mirror images of each other.

Question 12

Which of the following is the best condition for an SN1 reaction?

Accepted Answer

Tertiary alkyl halide in polar protic solvent

Question 13

Which of the following is the major product of the Markovnikov addition of HBr to 1-butene ($$\mathrm{CH_2$=CHCH_2CH_3}$$)?

Accepted Answer

$$\mathrm{2{-}bromobutane}$$

Question 14

Which of the following statements about epoxidation of alkenes is correct?

Accepted Answer

Epoxidation converts an alkene into a three-membered cyclic ether using a peracid.

Question 15

Which of the following best describes the relationship between cis- and trans-2-butene?

Accepted Answer

They are geometric (cis-trans) isomers.

Question 16

A student is asked to draw the mechanism for the acid-catalyzed addition of water to ethene ($$\mathrm{CH_2$=CH_2$}). $$Which is the correct first step?

Accepted Answer

Protonation of the alkene to form a carbocation intermediate

Question 17

Which of the following is the correct order of increasing nucleophilicity in polar aprotic solvents?

$$\mathrm{I^-}$$, $$\mathrm{Br^-}$$, $$\mathrm{Cl^-}$$, $$\mathrm{F^-}$$

Accepted Answer

$$\mathrm{F^-} \u003c \mathrm{Cl^-} \u003c \mathrm{Br^-} \u003c \mathrm{I^-}$$

Question 18

Which of the following best explains why the pKa of acetic acid ($$\mathrm{CH_3COOH}) is $$much lower than that of ethanol ($$\mathrm{CH_3CH_2OH}$$)?

Accepted Answer

The carboxylate anion is stabilized by resonance.

Question 19

Which of the following is the correct product for the bromination of cyclohexene ($$\mathrm{C_6H_{10}}) in $$water?

Accepted Answer

Trans-1-bromo-2-hydroxycyclohexane

CHE 251-003 Organic Chemistry I - Fall 2025 Syllabus and Study Guide

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