Organic Chemistry Practice Problems (Set 1)

Condensation polymerization joins monomers while eliminating a small molecule (most commonly water) as the new bond forms. The other choices are not typical by-products of condensation steps.

Ethanol (CH₃CH₂OH) is a primary alcohol because its –OH group is on a carbon attached to only one other carbon. Ethylene glycol and glycerol are polyhydric alcohols (diol/triol), and 2-butanol’s –OH is on a secondary carbon.

In ethyne (C₂H₂), the carbon–carbon triple bond contains three shared pairs of electrons (one σ bond and two π bonds) for a total of six shared electrons.

Carbon-14 is a radioactive isotope used as a tracer to investigate organic reaction mechanisms. Carbon-12 is stable (nonradioactive), and uranium isotopes are not typically used to label organic molecules.

Proteins are natural polymers (polypeptides made from amino acids), while nylon is a synthetic polymer (a polyamide). The other pairs are either both natural or both synthetic.

Primary alcohols oxidize to aldehydes. Secondary alcohols oxidize to ketones, and tertiary alcohols resist oxidation under similar conditions. Organic and inorganic acids are not oxidized to aldehydes.

Adding H₂ to C₂H₂ to form C₂H₆ is an addition (hydrogenation) reaction: hydrogen adds across the multiple bond, reducing the alkyne to an alkane.

Ethyne and acetylene are two names for the same compound (HC≡CH). Ethene is also called ethylene, and ethane is a different, saturated hydrocarbon.

Condensation polymerization links monomers while eliminating a small molecule—often water or methanol. This contrasts with addition polymerization, which adds monomers without loss of small molecules.

Ketones have a carbonyl group (C=O) bonded to two carbon groups (R–CO–R’). CH₃COCH₃ (acetone/2-propanone) fits this. CH₃COOH is a carboxylic acid, C₂H₅OH is an alcohol, and CH₃COOCH₃ is an ester.

All isotopes of hydrogen have one proton in the nucleus. Neutrons vary by isotope, and electrons can vary with ionization state.

The H–O bond in water involves shared electrons (covalent), but because oxygen is more electronegative than hydrogen, the bond is polar covalent.

In C₃H₅(OH)₃, the “H₅” contributes five hydrogens, and the three –OH groups contribute three more hydrogens to reach 8 total hydrogens.

An amphoteric substance can act as an acid or a base depending on conditions. Water is a classic example. “Neutral” describes pH, not acid–base behavior, and monomers/isomers are unrelated concepts.

Electrolytes produce ions in aqueous solution. Acetic acid (CH₃COOH) partially ionizes (weak electrolyte), whereas methanol, glycerol, and sucrose do not ionize appreciably (nonelectrolytes).

Organic acids contain the carboxyl (–COOH) functional group. Options with –OH but no –COOH are alcohols, and the sugars listed are not acids.

Alcoholic fermentation converts glucose to ethanol and carbon dioxide:

\(\text{C}_6\text{H}_12\text{O}_6 \rightarrow 2 \text{C}_2\text{H}_5\text{OH} + 2 \text{CO}_2\)

Thus CO₂ is produced along with ethanol.

CH₂CH₂ (ethene) adds H₂ across its double bond to become CH₃CH₃ (ethane). This hydrogenation is an addition reaction, not substitution, esterification, or fermentation.

Alkenes have the general formula C_nH_2n (one C=C). C₂H₄ and C₄H₈ both fit this and can each contain one double bond, whereas C₂H₂ is an alkyne and C₆H₆ is aromatic.

Some C₄H₈ isomers are cycloalkanes, but in the typical context here these formulas denote alkenes.

Fractional distillation separates hydrocarbons by differences in boiling point: shorter, less polarizable molecules boil at lower temperatures and rise higher in the column than longer, higher-boiling fractions.