SN2 SN1

Question 1

Steric hindrance

Answer 1

it is the congestion caused by the physical presence of ligands. The larger the ligand, the greater the hindrance. which will slow down the atom reaching the x.

Question 2

SN1 rate law

Answer 2

Rate = k[electrophile]

Question 3

SN2 rate law

Answer 3

Rate = k[nucleophile]×[electrophile]

Question 4

SN1 stereochemistry

Answer 4

racemization on reaction center

Question 5

SN2 stereochemistry

Answer 5

inversion on reaction center

Question 6

Electrophilic Substrate on sn1

Answer 6

tertiary 3° > secondary 2° > primary 1° and methyl

Question 7

Electrophilic Substrate on sn2

Answer 7

primary 1° and methyl > secondary 2° > tertiary 3°

Question 8

Nucleophile SN1

Answer 8

weak nucleophile, solvolysis

Question 9

Nucleophile SN2

Answer 9

strong nucleophile

Question 10

for SN2 what direction does the Nucleophile react?

Answer 10

180

Question 11

in SN2 is it the front or the back?

Answer 11

it is the back side

Question 12

draw the transition state

Answer 12

pentacoordinated carbon

Question 12

draw the transition state

Answer 12

pentacoordinated carbon

Question 13

Why is SN2 second ordered?

Answer 13

In the mechanism, the reaction proceeds in a single step that involves both nucleophile and the substrate, so increasing the concentration of either of them makes the possibility of collision increase, that explains the second-order kinetics of SN2 reaction. With both nucleophile attacking and leaving group leaving happen at the same time, SN2 is also said to be a concerted mechanism, concerted means simultaneous.

Question 14

in sn2 you must show

Answer 14

the arrows

Question 15

the highest point at the energy profile

Answer 15

the transition state

Question 16

what alkyl is most likely to go under sn2

Answer 16

methyl

Question 17

steric hindrance

Answer 17

Steric effect is the effect that based on the steric size or volume of a group. Because of the steric hinderance of bulky groups on the electrophilic carbon, it is less accessible for nucleophile to do back-side attack, so the SN2 reaction rate of secondary (2°) and tertiary (3°) substrates decreases dramatically. Actually the 3° substrates never go with SN2 reaction mechanism because the reaction rate too slow.

Question 18

Walden inversion.

Answer 18

the product get inverted comparing to that of the reactant, like an umbrella flipped inside out.

Question 19

SN2 leaving group

Answer 19

the less basic the nucleophile is the better the leaving group

Question 20

leaving group chart for SN2

Answer 20

(best leaving group) I–> Br–> Cl–> F– (weakest leaving group)

Question 21

Strong bases

Answer 21

Strong bases such as OH–, RO–, NH2–, R– are therefore very poor leaving groups and cannot go with nucleophilic substitution reactions. For OH– or RO– however, upon protonation they can be converted to neutral H2O or ROH molecules,

Question 22

bulky vs small

Answer 22

Smaller group is better nucleophile than bulky group.

Question 23

SN2 nucleophility

Answer 23

Nucleophilicity decrease across a period.

Question 24

what side can SN2 take place

Answer 24

from the back

Question 25

SP2 SN2

Answer 25

Bonds on sp2-hybridized carbons are inherently shorter and stronger than bonds on sp3-hybridized carbons, meaning that it is harder to break the C-X bond in these substrates. SN2 reactions of this type are unlikely also because the (hypothetical) electrophilic carbon is protected from nucleophilic attack by electron density in the p bond. SN1 reactions are highly unlikely, because the resulting carbocation intermediate, which would be sp-hybridized, would be very unstable (we’ll discuss the relative stability of carbocation intermediates in a later section of this module).

Question 26

the more basic

Answer 26

the more nucleophilic

Question 27

Electronegative elements are

Answer 27

less basic and less basic

Question 29

resonance effects on nucleophilicity

Answer 29

if the electron lone pair on a heteroatom is delocalized by resonance, it is inherently less reactive - meaning less nucleophilic, and also less basic.

Question 30

group 7 leaving group

Answer 30

As Size Increases, Basicity Decreases, Leaving Group Stability Increases:

In general, if we move from the top of the periodic table to the bottom of the periodic table as shown in the diagram below, the size of an atom will increase.

As size increases, basicity will decrease, meaning a species will be less likely to act as a base; that is, the species will be less likely to share its electrons.

Question 31

resonance

Answer 31

Resonance Decreases Basicity and Increases Leaving Group Stability

Question 32

SN2 solvent

Answer 32

SN2 reactions are faster in polar, aprotic solvents: those that lack hydrogen-bond donating capability. Below are several polar aprotic solvents that are commonly used in the laboratory:

Question 33

Frontside Orientation:

Answer 33

In a frontside orientation, the nucleophile approaches the electrophilic center on the same side as the leaving group. With frontside orientation, the stereochemistry of the product remains the same; that is, we have retention of configuration.

Question 34

sn1

Answer 34

the carbocation forms when the C-X bond breaks first, before the nucleophile approaches

Question 35

the carbocation is

Answer 35

sp2 hydridised
trigonal planar

Question 36

the carbocation has a

Answer 36

empty P orbital

Question 37

When the Nu attack in SN1

Answer 37

it becomes sp3 tetrahedral

Question 38

a racemic solution is formed in SN1 as

Answer 38

Because of this trigonal planar geometry, the nucleophile can approach the carbocation from either lobe of the empty p orbital (aka either side of the carbocation).

Question 39

the more stable the carbocation

Answer 39

the faster the reaction in SN1 as the activation energy decreases

Question 40

leaving groups

Answer 40

A good leaving group is a weak base because weak bases can hold the charge. They’re happy to leave with both electrons and in order for the leaving group to leave, it needs to be able to accept electrons