Exam 4

Question 1

Acetylide anions undergo Sn2 reactions with what degree substituted alkyl halide?

Answer 1

Primary (1’)

Question 2

Acetylide anions undergo E2 reactions with what degree substituted alkyl halide?

Answer 2

Secondary and tertiary (2’ and 3’)

Question 3

Terminal alkynes are readily converted to acetylide anions with strong bases such as NaNH2 and NaH.

Answer 3

These undergo Sn2 reaction for 1’ alkyl halides, and E2 reactions for 2’ and 3’ alkyl halides

Question 4

True/False: Acetylide anions are strong nucleophiles that open epoxide rings by an SN2 mechanism.

Answer 4

True

Question 5

What is another name for the product of a synthesis reaction?

Answer 5

Target compound

Question 6

What are the two categories used to design a synthesis?

Answer 6

1–Those that form new carbon–carbon bonds. 2–Those that convert one functional group into another—that is, functional group interconversions.

Question 7

What is a tautomer?

Answer 7

Tautomers are constitutional isomers that differ in the location of a double bond and a hydrogen atom. Two tautomers are in equilibrium with each other.

Question 8

What is an enol tautomer?

Answer 8

An enol tautomer has an O—H group bonded to a C==C.

Question 9

What is an keto tautomer?

Answer 9

A keto tautomer has a C=O and an additional C—H bond.

Question 10

What does it mean to be acid catalyzed in a reaction?

Answer 10

When the acid used to protonate an enol in step 1, is reformed in step 2

Question 11

When acetylide anions (which are strong Nu-) open epoxide rings via Sn2, which carbon do they attack ?

Answer 11

The least substituted carbon

Question 12

True/False: Two tautomers are in equilibrium with eachother

Answer 12

True

Question 13

What does the addition of H2O using H2O, H2SO4, and HgSO4 form?

Answer 13

methyl ketones from terminal alkynes

Question 14

What does the addition of H2O using BH3, then H2O2, HO form?

Answer 14

aldehydes from terminal alkynes

Question 15

Primary (1’) alcohols are oxidized to ______ or ______

Answer 15

Aldehydes or Carboxylic acids

Question 16

Secondary (2’) alcohols are oxidized to ________by replacing one C-H bond with a C-O bond.

Answer 16

Ketones

Question 17

Do tertiary alcohols normally undergo oxidation reactions?

Answer 17

No

Question 18

Name three common strong, but non-selective oxidants used in aqueous acid (H₂SO₄ + H₂O)

Answer 18

CrO₃

Na₂Cr₂O₇

K₂Cr₂O₇

Any of the Cr⁶⁺ oxidants effectively oxidize alcohols to ketones

Question 19

What is PCC soluble in?

Answer 19

CH₂Cl₂

Question 20

Why is PCC useful?

Answer 20

It can be used without acid present, making it a more selectvie, milder oxidant

Question 21

What is often used to oxidize a primary (1’) alcohol to an aldehyde (RCHO)?

Answer 21

PCC in CH₂Cl₂

Question 22

What is used to oxidize a primary alcohol to a carboxylic acid (RCOOH) under harsher reaction conditions?

Answer 22

CrO₃

Na₂Cr₂O₇

K₂Cr₂O₇

in the presence of H₂O and H₂SO₄

Question 23

What are the three steps needed to oxidize a primary alcohol to a carboxylic acid?

Answer 23

1-Oxidize the alcohol to an aldehyde

2-React the aldehyde with water

3-Further oxidize to the carboxylic acid

Question 24

What is an enantioselective reaction?

Answer 24

One in which one enantiomer is formed predominantly or exclusively

Question 25

What type of reaction converts an achiral starting material into predominantly one enantiomer?

Answer 25

An asymmetric reaction

Question 26

Where does epoxidation with (-) DET add an oxygen?

Answer 26

From **_above_** the plane

Question 27

Where does epoxidation with (+) DET add an oxygen?

Answer 27

From **_below_** the plane

Question 28

What is ozonolysis?

Answer 28

A two-step form of oxidative cleavage using ozone (O₃).

Question 29

What molecule(s) result from the oxidative cleavage of a terminal alkyne?

Answer 29

Carboxylic acid and CO₂

Question 30

What molecule(s) result from the oxidative cleavage of an internal alkyne?

Answer 30

2 Carboxylic acids