Carbonyl Chemistry

Question 1

Distinguish between stereochemistry for SN1 vs SN2

Answer 1

SN1: Racemization of configuration
SN2: Inversion of configuration

Question 2

Compare the kinetics (rate law) for SN1 vs SN2 reactions

Answer 2

SN1 : Rate = k [electrophile)
SN2 : Rate = k [nucleophile] electrophile]

Question 3

What kind of solvents are used for SN1 vs SN2 reactions. Give examples

Answer 3

SN1 : polar Protic ex: water, ROH
SN2: polar APROTIC ex: DMSO, DMFAcetone

Question 4

explain mechanism for SN1 and SN2 reactions

Answer 4

SN1: form CARBOCATION intermediate
SN2; Concerted BACKSIDE attack; pentavalent transition state

Question 5

What is the priority of chemical groups for substrate structure?

Answer 5

SN1: Tertiary>secondary> primary > methyl
SN2: Methyl> primary> > secondary > tertiary

Question 6

What are properties of diasteromers ? What kind of lab technique can be used to separate them?

Answer 6

Diastereomers: have different physical properties
The compounds will likely have very similar polarities and boiling points. Fractional distillation will be used since it is a is a separation technique designed to purify compounds with similar boiling points,

Question 7

what does regioselective mean?

Answer 7

regioselective: describes reactions that select for one structural isomer, becoming the major product, when other structural isomers are possible, becoming very minor products

Question 8

What kind of lab techniques are TLC and H-NMR?

Answer 8

Identification techniques

Question 9

What kind of technique is column chromatography ? How does it work?

Answer 9

Column chromatography- SEPARATION technique used to separate structures by differences in polarity

Question 10

What is a lewis acid?

Answer 10

Lewis acid- electron ACCEPTOR

Question 11

what do nucleophiles and lewis bases share ?

Answer 11

A nucleophile is also a lewis base (donates electrons)

Question 12

What does the SN1 reaction depend on ?

Answer 12

SN1 reaction depends on formation of carbocation

Question 13

what happens to rate of reaction if a catalyst lowers activation energy of second step of reaction in SN1? Explain why

Answer 13

The overall rate of reaction will Not be altered
If the catalyst lowers the Ea of the second step of the reaction, that elementary step will be faster. However, in an SN1 reaction the rate is dependent on the formation of the carbocation, the first and rate-limiting step.
Because the catalyst does not have any effect on the rate-limiting step, it will not alter the kinetics of the overall reaction.

Question 14

Which lab techniques can be used to separate volatile compounds (high boiling points) ?

Answer 14

Fractional distillation and Gas chromatography can both be used

Question 15

What can Electrophoresis be used for ?

Answer 15

Electrophoresis can be used to separate molecules based on CHARGE as well as SIZE
(hence used to seperate cross-linked DNA molecules )

Question 16

Which reagent should be used to generate sodium ethoxide from ethanol? Explain why

Answer 16

NaNH2 should be used, since the base used should be significantly STRONGER than the conjugate base that is being generated.
Deprotonating EtOH requires a very strong base because the conjugate base (ethoxide) of ethanol is itself strong. The strongest base of the answer options is sodium amide

Question 17

What is the only Reagent that can be used to form a new carbon-carbon bond ?

Answer 17

GRIGNARD REAGENTS (RMGBR as nucleophile)