Organic Chemistry Flashcards

Which of the following correctly describes the relationship between enthalpy of combustion and molecular structure for straight-chain alkanes?

Answer: Enthalpy of combustion increases as chain length increases.

Each additional CH2 unit contributes approximately 659 kJ/mol to the enthalpy of combustion, so longer chains release more energy.

Which type of reaction converts an alkyl halide into an alkene by treatment with a strong, bulky base such as KOtBu?

Answer: E2

Bulky bases favor E2 elimination because steric hindrance prevents the nucleophilic SN2 pathway.

What is the term for the energy difference between reactants and the transition state in a reaction?

Answer: Activation energy (Ea)

Activation energy is the minimum energy required to reach the transition state and is the energy barrier of the reaction.

Carboxylic acid derivatives in decreasing order of reactivity toward nucleophilic acyl substitution are:

Answer: Acid chloride > anhydride > ester > amide

Reactivity decreases as the leaving group ability decreases: Cl⁻ > RCOO⁻ > RO⁻ > NH2⁻.

What product is formed when a primary amine reacts with excess methyl iodide followed by Ag2O/H2O and heat?

Answer: The least substituted alkene (Hofmann elimination product)

Hofmann exhaustive methylation converts a quaternary ammonium hydroxide to the least hindered alkene via elimination.

Which orbital interaction is responsible for the aromatic stability of benzene?

Answer: Continuous cyclic overlap of six p orbitals forming delocalized π electrons

Benzene's six p orbitals overlap continuously around the ring, delocalizing six π electrons and conferring exceptional stability.

An unknown compound shows a broad O–H stretch near 3300 cm⁻¹ and a C=O stretch at 1710 cm⁻¹ in its IR spectrum. What functional group is most likely present?

Answer: Carboxylic acid

A broad O–H stretch combined with a carbonyl peak near 1710 cm⁻¹ is the hallmark IR signature of a carboxylic acid.