7. Reaction of Alkyl halide

Question 1

Reactions of Alkyl halide involves

Answer 1

Substitution
Reaction

Nucleophilic Reactions
-Nucleophilic Substitution Bimolecular (SN2)

Nucleophilic Substitution Unimolecular (SN1)

Question 2

Substitution
Reaction

Any atom on the alkyl halide is
replaced with another group. T or F

Answer 2

False. HALOGEN atom on the alkyl halide is

replaced with another group

Question 3

Halogen is more electronegative
than carbon, the C-X bond breaks
heterolytically and X- leaves. T or F?

Answer 3

True. The group replacing X- is a NUCLROPHILE

Question 4

Nucleophilic Substitution Bimolecular (SN2) is dependent on?

Answer 4

Dependent on the CONCENTRATION (M) of the TWO REACTANTS - Reaction Rate = k[A][B]

Question 5

Nucleophilic Substitution Bimolecular (SN2) has how many steps?

Answer 5

single-step thus, there is no intermediates

Question 6

Nucleophilic Substitution Bimolecular (SN2) configuration of reactant and products?

Answer 6

Product has the PPOSITE configuration of the

reactant. Due to the attack at the opposite of the halogen or leaving group.

Question 7

SN2 Mechanism: Factors

Affecting the Rate

Answer 7

1. Substrate
2. Nucleophile
3. Leaving Group
4. Solvent

Question 8

Substrate must be sterically hindered substrate, the

faster reaction. T or F?

Answer 8

Substrate must be LESS sterically hindered substrate, the faster reaction

Question 9

Nucleophilicity of a molecule
depends on the substrate, solvent and reactant
concentrations.

Answer 9

True. SN2 mechanism depends on the concentration of all reactants.

Question 10

Best leaving groups are those that cannot stabilize

the negative charge in the transition state. T or F?

Answer 10

Best leaving groups are those that BEST stabilize
the negative charge in the TRANSITION STATE as an effect,
there will be faster reaction.

Ideally, weakest bases

Question 11

Polar protic solvents, which are polar and contains –OH or –NH group are the best in SN2 mechanism

Answer 11

polar APROTIC solvents, which are polar but DO NOT HAVE –OH or –NH group are the best in SN2 mechanism

Question 12

Nucleophilic Substitution Unimolecular (SN1) is dependent only on?

Answer 12

Rate is dependent only on the substrate (alkyl halide) and independent of the nucleophile
concentration
Rate = k[A]

Question 13

Nucleophilic Substitution Unimolecular (SN1) has how many steps?

Answer 13

Two. Involve formation of carbocation intermediate followed by the losing of proton.

Question 14

Nucleophilic Substitution Unimolecular (SN1) has what configuration in reactant and product.

Answer 14

Product is
optically active
because 50:50
mixture of +/- results. RACEMIC

Question 15

Factors

Affecting the Rate of SN1 Mechanism in the substrate?

Answer 15

Stability of the carbocation greatly favors the

reaction. Must have a reactive halides

Question 16

Factors

Affecting the Rate of SN1 Mechanism in the leaving group.

Answer 16

most stable, best leaving group

Question 17

Factors

Affecting the Rate of SN1 Mechanism in the Nucleophile: Affects the reaction rate. T or F?

Answer 17

False. DOES NOT affect reaction rate because SN1 is substrate concentration dependent.

BUT it must be non basic to prevent a
competitive elimination of HX

Question 18

Factors
Affecting the Rate of SN1 Mechanism in the Solvent: effect is due to stabilization or destabilization of the
transition state T or F?

What solvent is best?

Answer 18

True.

Polar protic solvent is highly favored in this reaction. Contains OH and NH2

Question 19

Elimination Reactions types:

Answer 19

1. Elimination Unimolecular (E1)
2. Elimination Bimolecular (E2)
   - Periplanar Geometry
3. Elimination unimolecular conjugate base (E1cB)

Question 20

Elimination Unimolecular (E1) is similar so SN1 and follows what rule in formation of products?

Answer 20

More stable product is formed
(Zaitsev’s rule) and follows a 1st order kinetics
- Geometrical requirement isn’t
required

Question 21

Elimination Bimolecular (E2)
C-H and C-X bonds
do not break simultaneously, giving the alkene in a two step
process.

Answer 21

C-H and C-X bonds
break SIMULTANEOUSLY giving the alkene in a SINGLE
process. Similar to SN2.

Question 22

Elimination unimolecular conjugate base (E1cB)

C-H bond breaks first giving a carbanion intermediate
that loses –X giving the alkene. T or F?

Answer 22

True. This usually occur in biological reactions

Question 23

Elimination unimolecular conjugate base (E1cB) is common to what substrates?

Answer 23

substrates with POOR LEAVING GROUP
such as –OH, two carbons removed from a carbonyl
group, as in HO-C-CH-C=O