Ch. 17 - Intro to Carbonyl Chemistry

Question 1

What is an acyl group?

Answer 1

RC=O

Question 2

What are the two classifications of carbonyl compounds?

Answer 2

acyl groups that have a LG (attached to another EN atom group that can be replaced) [includes Cl, OC=O, OH, OR, NH2/R/R2]

acyl group without a LG (aldehydes/ketones)

Question 3

Rank the following in order of LG ability: OR, NH2, Cl, OC=O, OH,

Answer 3

worst to best

NH2, OR, OH, OC=O, Cl

Question 4

Can aldehydes and ketones undergo nucleophilic substitution?

Answer 4

no, they do not have a leaving group

Question 5

Is the carbon of a carbonyl nucleophilic or electrophilic? Why?

Answer 5

electrophilic because oxygen is more EN than carbon and pulls e- density

Question 6

Why can’t H or R group be a LG?

Answer 6

H and R groups are weak acids so their conjugate bases are hydride and -R which are strong bases; this is not favored in equilibirum

Question 7

Is an aldehyde or ketone more reactive? Why?

Answer 7

aldehyde

1) ketone is more sterically hindered (bigger R groups decrease reactivity)
2) ketone has electron donating groups which decrease carbon electrophilicity

Question 8

Does NaBH4 and LAH reduce alkenes or alkynes?

Answer 8

No, NaBH4 is more selective. It only reduces aldehydes, ketones and acid chlorides

Question 9

Does water have to be added separately in a reaction with NaBH4 or LAH?

Answer 9

LAH, it could be explosive

Question 10

What carbonyl compounds with LAH reduce?

Answer 10

LAH is a strong reductant, it will reduce all carbonyl compounds

Question 11

What does H2 Pd/C or Raney Nickel reduce? Which of these groups will it reduce first?

Answer 11

Reduces aldehydes, ketones and alkenes; will reduce alkenes first

Question 12

What is LiAlH(OtBu)3 used to reduce? What is the reduction product? Finally, why does this work?

Answer 12

Used to reduce acid chlorides to product aldehydes. This reductant works for reducing to an aldehyde because it only has one H source and has three bulky groups.

Question 13

Does Lindlar’s cat or NaNH3 reduce aldehydes or ketones?

Answer 13

No, just alkynes

Question 14

What is DIBAL-H used to reduce? What is the reduction product and why does this reductant work?

Answer 14

Reduces esters and carboxylic acids to aldehydes. Reduces to an aldehyde and not fully to an alcohol because DIBAL-H only has one hydride source and also has two bulky groups.

Question 15

In order to “stop at the aldehyde” what must be used?

Answer 15

A milder reducing agent

Question 16

What are examples of milder reducing agents?

Answer 16

LiAlH(OtBu)3 (less nucleophilic) and DIBAL-H (bulky groups)

Question 17

What is a lactone?

Answer 17

A cyclic ester

Question 18

What happens when cyclic ester (lactone) reacts with DIBAL-H? What happens when a cyclic ester reacts with LAH?

Answer 18

DIBALH: Gives a chain with an aldehyde on one end and an alcohol on the other
LAH: Gives a chain with alcohols on either end

Question 19

What is a lactam?

Answer 19

a cyclic amide

Question 20

What is an important intermediate of reduction of amides?

Answer 20

Imine

Question 21

Can NaBH4 reduce carb acids, esters and amides?

Answer 21

No, LAH is needed for these compounds because they have worst leaving groups and NaBH4 is too weak

Question 22

What will happen to CN (has triple bond) if it reacts with H2 Pd/C or NaBH4 and water?

Answer 22

It is reduced all the way to CH2NH2

Question 23

What are organometallic compounds?

Answer 23

Reagents that contain carbon bonded to a metal and sort of act like carbanions

Question 24

Is the metal-adjacent carbon of an organometallic reagent nucleophilic or electrophilic?

Answer 24

Nucleophilic, the metal is less EN then the carbon and therefore has a partial positive charge.

Question 25

How are organolithium compounds made?

Answer 25

halide + 2Li and hexanes

Li replaces halide

Question 26

How are organomagnesium (Grignard) compounds made?

Answer 26

halide + Mg(s) and ether

Mg inserts btw halide and R

Question 27

How are organocuprate compounds made?

Answer 27

halide + CuI and THF

two halid groups add to Cu

Question 28

What does the reactivity of organometallic reagents depend on? What are the reactivities of the organometallic reagents studied?

Answer 28

More polar = more reactive

Most to least reactive: R-Li, R-MgX, R2-CuLi

Question 29

Why can organocuprates hold two R groups?

Answer 29

They have a more accommodating valence shell.

Question 30

Are organometallic reagents acids or bases?

Answer 30

Can act as strong bases and therefore can readily abstract a proton from water or OH group

Question 31

What are alpha-beta unsaturated carbonyl compounds?

Answer 31

conjugated molecules with a carbonyl group and a C=C that is alpha to the carbonyl group

Question 32

How many reactive sites does an alpha-beta unsaturated compound have?

Answer 32

two electrophilic sites; one at the carbonyl carbon and one on the beta carbon (far end of alkene pi bond)

Question 33

Why must protective groups be used for some reactions?

Answer 33

Rapid acid-base reactions can occur between certain reagents (esp organometallics) and OH groups. If this group is not desired to be reduced, a protective group can be used to keep it from interacting.

Question 34

What is the most common protector group and accompanying deprotector?

Answer 34

protector: TBDMSCl with imidazole
deprotector: TBAF

Question 35

When reacting with Grignard reagents, does an acyl chloride or ester have a fast collapse?

Answer 35

acyl chloride; has better LG

Question 36

What carbon is attacked by the nucleophile for an epoxide in acidic and basic conditions?

Answer 36

acidic: most sub’d carbon
basic: least sub’d carbon

Question 37

What are alpha hydroxy alkynes?

Answer 37

Alkyne functional group that is bonded to a carbon bearing an OH group