Reaction mechanisms

Question 1

What are the likely products of the reaction between OH– and CH3Br?

Answer 1

CH3OH + Br–

Question 2

What is the form of the rate equation for an SN1 reaction?

Answer 2

rate = k[substrate]

Question 3

What is the name given to a substance that occurs in a reaction mechanism as a short-lived and reactive species that cannot be isolated?

Answer 3

An intermediate

Question 4

A chemical species that “seeks out” and “attacks” electron-deficient atoms is called:

Answer 4

A nucleophile

Question 5

Polar bonds are most likely to arise when the atoms in question have different

Answer 5

Electronegativities

Question 6

For a certain nucleophilic substitution reaction, the rate = k[substrate][nucleophile]. What does this imply about the mechanism?

Answer 6

an SN2 reaction (by definition)

Question 7

A nucleophilic substitution reaction takes place with a chiral substrate and forms a racemic product. What does this imply about the mechanism?

Answer 7

an SN1 reaction, via a planar carbocation

Question 8

In an SN2 reaction, a chiral substrate (R configuration for the chiral C atom) reacts with a nucleophile to form a chiral product with a(n) ____ configuration.

Answer 8

S configuration (i.e. inversion)

Question 9

A carbocation has now many valence electrons?

Answer 9

6

Question 10

What is a common competing reaction for a nucleophilic substitution reaction?

Answer 10

elimination

Question 11

In an elimination reaction, the substrate is R2CH–CH(OH)R2. What are the products?

Answer 11

R2C=CR2 + H2O

Question 12

Which bonds are broken in an elimination reaction?

Answer 12

C–H and C–X (e.g. X = OH or Br)

Question 13

Which bonds are formed in an elimination reaction?

Answer 13

C=C (from C–C) and HX

Question 14

What is the form of the rate equation for an E1 reaction

Answer 14

Rate = k[substrate]

Question 15

What property of a nucleophile will tend to favour elimination over substitution

Answer 15

if it’s a strong base

Question 16

Which of the following nucleophiles is more likely to lead to an elimination reaction?

a) OH–
b) Br–
c) Cl–
d) SH–

Answer 16

a) OH–

Question 17

What is the general form of an addition reaction?

Answer 17

R2C=CR2 + XY → R2CX–CYR2

Question 18

Which bonds are broken in an addition reaction?

Answer 18

C=C (to form C–C) and X–Y

Question 19

In the first step of an addition reaction, what is the nucleophile?

Answer 19

the electron-rich C=C double bond

Question 20

What is the usual intermediate in an addition reaction?

Answer 20

a carbocation

Question 21

Who’s rule predicts the sense of addition of HBr to an unsymmetrical alkene?

Answer 21

Markovnikov’s

Question 22

What is the expected majority product for the addition of HBr to propene?

Answer 22

H3C–CHBr–CH3

Question 23

In a radical reaction, what usually occurs first?

Answer 23

homolytic bond cleavage

Question 24

Which of the following bonds is most likely to be homolytically cleaved by visible light?

a) C–H in CH4
b) O–O in O2
c) N–N in N2
d) Br–Br in Br2

Answer 24

Br–Br in Br2

Question 25

The first step of a radical reaction is called

Answer 25

Initiation

Question 26

What happens in the termination stage of a radical reaction?

Answer 26

two radicals combine together

Question 27

Which alkyl radical is most stable?

Answer 27

Tertiary

Question 28

The schematic reaction “large molecule + water → two smaller molecules” is called: a) Hydration b) Hydrolysis c) Disruption d) Dissolution

Answer 28

Hydrolysis

Question 29

Which of the following definitions of oxidation of organic molecules is not correct? a) Removal of electrons b) Addition of oxygen c) Removal of hydrogen d) Conversion of a C=C double bond to a C–C single bond.

Answer 29

Conversion of a C=C double bond to a C–C single bond.

Question 30

Which of the following transformations is not an oxidation? a) Primary alcohol → aldehyde b) Secondary alcohol → ketone c) Primary alcohol → carboxylic acid d) Carboxylic acid + alcohol → ester

Answer 30

d) Carboxylic acid + alcohol → ester

Question 31

Which of the following reagents is a reducing agent? a) LiAlH4 b) H2CrO4 c) O2 d) He

Answer 31

a) LiAlH4

Question 32

Which is the reduced form; NADH or NAD+?

Answer 32

NADH