Ch 10

Question 1

What type of mechanism is required to convert OH to alkyl halides using PBr₃ or PCl₃?

Answer 1

S_N2

Question 2

What type of Carbon (1º, 2º, and/or 3º) is required to convert OH to alkyl halides using PBr₃ or PCl₃?

Answer 2

1º or 2º Carbon

Question 3

Does an irreversible reaction have a large or small delta G?

Answer 3

Large delta G

Question 4

Does an irreversible reaction have a large or small Keq?

Answer 4

Large Keq

Question 5

Does a reversible reaction have a large or small delta G?

Answer 5

Small delta G

Question 6

Does a reversible reaction have a large Keq, small Keq, or Keq close to 1?

Answer 6

Keq close to 1

Question 7

Which will react fastest in S_N2?

methyl, 1º, 2º, or 3º

Answer 7

methyl is fastest

(then 1º, then 2º, then 3º)

Question 8

Which will react slowest in S_N2?

methyl, 1º, 2º, or 3º

Answer 8

3º is slowest

Question 9

Which is faster, kinetic or thermodynamic reactions?

Answer 9

Kinetic reactions are faster

Question 10

Are kinetic reactions reversible or irreversible?

Answer 10

Kinetic reactions are irreversible

Question 11

For a kinetic reaction, do you use LDA or t-Butoxide?

Answer 11

LDA

Question 12

Does LDA prefer the more substituted side or less sibstituted alpha Carbon?

Answer 12

LDA prefers the less substituted Carbon

Question 13

Are thermodynamic reactions reversible or irreversible?

Answer 13

Thermodynamic reactions are reversible

Question 14

For a thermodynamic reaction do you use LDA or t-Butoxide?

Answer 14

Use t-Butoxide

Question 15

Does t-butoxide (-OC(CH₃)₃) prefer the more or less substituted alpha carbon?

Answer 15

t-Butoxide prefers the more subsitituted carbon

Question 16

What do you need to open an epoxide?

(Strong or weak nucleophile / acidic or basic conditions)

Answer 16

A strong nucleophile and basic or neutral conditions

Question 17

What is Exhaustive Halogenation?

(i.e. Polyhalogenation)

Answer 17

when every alpha hydrogen is replaced by a halogen atom

Question 18

Do kinetic reactions prefer the more or less substituted alpha carbon?

Answer 18

Kinetic reactions prefer the less substituted alpha carbon

Question 19

Do thermodynamic reactions prefer the more or less substituted alpha carbon?

Answer 19

Thermodynamic reactions prefer the more sustituted alpha carbon

Question 20

To control an epoxide, will basic/neutral contitions cause the nucleophile to attack the more or less substituted carbon?

Answer 20

It will cause the nucleophile to attck the less sibstituted carbon

Question 21

To control an epoxide, will acidic contitions cause the nucleophile to attack the more or less substituted carbon?

Answer 21

the nucleophile will attack the more subsituted carbon

Question 22

If you have an sp² carbon, will you have an E1 or S_N2 reaction?

Answer 22

an E1

(S_N2 can’t happen on an sp² carbon)

Question 23

what reaction conditions could you use to do exhaustive Halogenation?

Answer 23

Cl₂ (excess)

NaOH

Question 24

When opening an epoxide in acidic conditions, what is the first step in the reaction?

Answer 24

A proton transfer to the Oxygen in the epoxide

Question 25

When using PBr₃ or PCl₃ do you expect to see an inversion of stereochemistry?

Answer 25

yes!

Question 26

What reaction conditions could you use to do Acid Promoted Halogenation?

Answer 26

HOAc

Br₂

Question 27

What is Acid Promoted Halogenation?

Answer 27

Only one alpha hydrogen is replaced with a halogen atom

Question 28

What bases can you use for Alkyne Elimination?

Answer 28

NaNH₂ (-NH₂)

NaH (-H)

Question 29

How many equivalents of a base must you use for a terminal alkyne elimation?

Answer 29

1 equivalent of base per π bond formed PLUS one equivalent to account for the proton transfer

Question 30

Explain why an epoxide reacts when treated with an alkoxide but larger rings do not

Answer 30

This is due to ring strain

Epoxides have a high amount of ring strain and can in turn behave as a substrate in an S_N2 reaction. Larger rings have much less ring strain and are more stable.

Question 31

Is an alkene more stable when it is more substituted or when it is less substituted?

Answer 31

More substituted alkene = more stable