Ch 20 Aldehydes And Ketones

Question 0

How do you name an aldehyde

Answer 0

-al,the number one carbon is the carbonyl carbon. Cyclic aldehydes are named carbaldehyde

Question 1

What happens when you protonate a ketone?

Answer 1

It is subject to attack by a weak Nu- because it become more electrophilic

Question 2

How do you name a ketone?

Answer 2

-one, alkyl alkyl naming ,position with locant

Question 3

How do you convert a primary alcohol into an aldehyde?13.10 draw several reactions

Answer 3

PCC/CH2Cl2-treatment with a strong oxidizing agent

Question 4

Ozonolysis of Alkenes 9.11 draw several reactions

Answer 4

1)O3, 2)DMS,ozonolysis will Cleave a double bond.

Question 5

How does resonace effect the electrophilicity of a carbonyl group? Draw the resonance structure.

Answer 5

One of the resonance structures exhibits a positive charge on the carbon atom, indicating that the carbon atom is deficient in electron density (d+)

Question 6

How does induction effect the electrophilicity of a carbonyl group?

Answer 6

Inductive effects also render the carbon atom deficient
in electron density. As a result, this carbon atom is particularly electrophilic and is susceptible to attack by a nucleophile.

Question 7

In general why are aldehydes more reactivce than ketones?

Answer 7

1. Steric effects. A ketone has two alkyl groups (one on either side of the carbonyl) that contribute to steric interactions in the transition state of a nucleophilic attack. In contrast, an aldehyde has only one alkyl group, so the transition state is less crowded and lower in energy.
2. Electronic effects. Recall that alkyl groups are electron donating. A ketone has two electrondonating alkyl groups that can stabilize the d+ on the carbon atom of the carbonyl group. In contrast, aldehydes have only one electron-donating group

The d+ charge of an aldehyde is less stabilized than a ketone. As a result, aldehydes are more electrophilic than ketones and therefore more reactive.

Question 8

What are the step in the nucleophilic addation under basic conditions? Draw the mechanism.

Answer 8

Question 9

What are the step in the nucleophilic addation under acidic conditions? Draw the mechanism.

Answer 9

Question 10

What is a hydrate? How is one formed?

Answer 10

When a aldehyde or ketone is treatedwith water, the carbonyl group can be converted into a hydrate. A hydrate has two OH groups.

Question 11

In a Hydrate formation where does the equilibrium postion sit? What are the exception?

Answer 11

The position of equilibrium generally favors the carbonyl group rather than the hydrate, except in thecase of very simple aldehydes, such as formaldehyde:

Question 12

What are the step in a base catalyzed hydration? Draw the Mechanism

Answer 12

Question 13

What are the step in a acid catalyzed hydration? Draw the Mechanism

Answer 13

Question 14

What is an acetal and how is it formed? What are the common acids used?

Answer 14

In acidic cinditions and aldehyde or ketone will react with to molecules of alcohol to from an acetal.

TsOH and H₂SO₄(sulfuric acid ) are the commonacids used.

Question 15

Why is an acid catalyst used in an acetal formation.

Answer 15

the acid catalyst serves an important role in this reaction. Specifically, in the presence of an acid, the carbonyl group is protonated, rendering the carbon atom even more electrophilic.
This is necessary because the nucleophile (an alcohol) is weak; it reacts with the carbonyl group more rapidly if the carbonyl group is first protonated.

Question 16

What are the step to form an acetal?

Answer 16

The first three steps produce an intermediate called a hemiacetal and (2) the last four steps convert the hemiacetal into an acetal:

Question 17

Why are acetals good protectiong groups?

Answer 17

Acetal formation is a reversible process that can be controlled by carefully choosing reagents and conditions. acetal formation is favored by removal of water. To convert an acetal back into the corresponding aldehyde or ketone, it is simply treated with water in the presence of an acid catalyst. In this way, acetals can be used to protect ketones or aldehydes.

LAH would reduce everything

Question 18

How is an imine formed?

Answer 18

in mildly acidic conditions, an aldehyde or ketone will react with a primary amine to from an imine.

Question 19

What is the mech for a imine formation?

Answer 19

(1) The first three steps produce an intermediate called a carbinolamine
(2) the last three steps convert the carbinolamine into an imine:

Question 20

How is an oxime formed?

Answer 20

with HO-NH₂ and an acid catalyst. With the same mech as an imine formation

Question 21

How is a hydrazone formed?

Answer 21

with H₂N-NH₂ and an acid catalyst. the mech is the same as an imine formation.

Question 22

How is an emamine formed?

Answer 22

in acidic conditions, an aldehyde or ketone will react with a secondary amine to from an enamine.

Question 23

What is a Wolff-Kishner Reduction?

Answer 23

the reduction of a hydrazone to an alkane under strong basic conditions and heat.

this transformation provides a two step procedure for reducing a ketone to an alkane.

Question 24

How are acetals,imines and enamines

Answer 24

acetals are hydrolized with aqueous acid to afford the corresponding aldehyde or ketone and alcohol imines and enamines also undergo hydrolysis when treated with aqueous acid to form ketone.

Question 25

How are thiosacetal formed?

Answer 25

in acidic conditions and aldehyde or ketone will react with two equivalents of a thiol to form a thioacetal. The mech is analogous to acetal formation.

Question 26

What is Raney nickel and what does it do?

Answer 26

When treated with Raney nickel, thioacetals undergo desulfurization, yielding an alkane. Raney Ni is a porous, Ni-Al alloy, in which the surface has adsorbed hydrogen atoms.

Question 27

What happen when an aldehyde or ketone is treated with a hydride reducing agent? What is the mech

Answer 27

When treated with a hydride reducing agent, such as lithium aluminum hydride (LAH) or sodium borohydride (NaBH4), aldehydes and ketones are reduced to alcohols.

Question 28

What happens when an aldehyde or ketone is treated with an aldehyde or ketone? What is the Mech

Answer 28

When treated with a Grignard reagent, aldehydes and ketones are converted into alcohols, accompanied by the formation of a new C-C bond Grignard reactions are not reversible because carbanions generally do not function as leaving groups. Notice that the first step of the mechanism (nucleophilic attack) is shown with an irreversible reaction arrow to signify that the reverse process is insignificant.

Question 29

What is a cyanohydrin and how is one formed?

Answer 29

When treated with hydrogen cyanide (HCN), aldehydes and ketones are converted into cyanohydrins, which are characterized by the presence of a cyano group and a hydroxyl group connected to the same carbon atom. In the presence of a catalytic amount of base, a small amount of hydrogen cyanide is deprotonated to give cyanide ions, which catalyze the reaction

Question 30

Why are cyanohydrins useful in syntheses?

Answer 30

the cyano group can be further treated to yield a range of products. In the first example, the cyano group is reduced to an amino group. In the second example, the cyano group is hydrolyzed to give a carboxylic acid.

Question 31

What is the Witting reaction?

Answer 31

This reaction can be used to convert a ketone into an alkene by forming a new C-C bond at the location of the carbonyl group. The phosphorus-containing reagent that accomplishes this transformation is called a phosphorus ylide. An ylide is a neutral molecule that contains a negatively charged atom (C- in this case) directly attached to a positively charged heteroatom (P+ in this case).

Question 32

What reagent can be used to convert a secondary alcohol into a ketone

Answer 32

Na₂Cr₂O₇/H₂SO₄,H₂O A variety of stong or mild oxidizing agents can be used to oxidize secondary alchols

Question 33

What will an acid catalyzed hydration of terminal alkynes form

Answer 33

H₂SO₄,H₂O/HgSO₄ this procedure results in a markovnikov addition of water accross the pi bond, followed by tautomerization to form a methyl ketone

Question 34

draw a Friedel-crafts acylation of benzene

Answer 34

Question 35

When treated with a peroxy acid, ketone can be converted into \_\_\_\_.

Answer 35

ester via the insertion of an oxygen atom

Question 36

lactone can formed from cylclic ketone and \_\_\_

Answer 36

peroxy acid

Question 37

an unsymmertical ketone is treated with a peroxy acid to forms a regioselective ester. Why

Answer 37

because isopropyl group migrates more rapidly than the methyl group during the rearrangentment step of the mech , migratory aptitude -the migration rates of different groups. H\>3\>2,Ph\>1\>methyl

Question 38

when benzylic aldehyde is treated with preoxy acid what is formed

Answer 38

benzoic acid