MS MS in Chemistry 3

Question 1

In an SN2 reaction, which substrate undergoes the fastest substitution?

Accepted Answer

Primary alkyl halide

Answer

Tertiary alkyl halide

Answer

Secondary alkyl halide

Answer

Neopentyl bromide

Question 2

Which reagent converts a primary alcohol to an aldehyde without further oxidation to a carboxylic acid?

Accepted Answer

PCC (pyridinium chlorochromate) in CH2Cl2

Answer

KMnO4 in acidic solution

Answer

K2Cr2O7 in H2SO4

Answer

Jones reagent (CrO3/H2SO4)

Question 3

The Diels-Alder reaction is classified as a [4+2] cycloaddition because it involves:

Accepted Answer

A 4π diene and a 2π dienophile

Answer

4 reactants and 2 products

Answer

4 single bonds and 2 double bonds formed

Answer

4 carbons and 2 heteroatoms

Question 4

Which amino acid side chain can form a disulfide bond, contributing to protein tertiary structure?

Accepted Answer

Cysteine

Answer

Serine

Answer

Threonine

Answer

Methionine

Question 5

In enzyme kinetics, the Michaelis constant Km represents:

Accepted Answer

The substrate concentration at which reaction velocity is half of Vmax

Answer

The maximum reaction velocity

Answer

The enzyme turnover number

Answer

The inhibitor dissociation constant

Question 6

Which polymer synthesis mechanism produces a broad molecular weight distribution (high dispersity Đ > 1.5) due to rapid chain initiation and slow termination steps?

Accepted Answer

Free-radical chain-growth polymerization

Answer

Living anionic polymerization

Answer

Ring-opening metathesis polymerization (ROMP)

Answer

Atom transfer radical polymerization (ATRP)

Question 7

The Hückel rule states that monocyclic, planar, fully conjugated systems are aromatic when they contain:

Accepted Answer

(4n+2) π electrons where n is a non-negative integer

Answer

Any even number of π electrons

Answer

(4n) π electrons where n is a positive integer

Answer

Exactly 6 π electrons only