Week 2

Question 1

Aldehyde

Answer 1

Double bonded oxygen to a carbon which is attached to one carbon and one hydrogen

Question 2

Ketone

Answer 2

Double bonded oxygen attached to a carbon which is attached to two other carbons

Question 3

Aldehyde naming

Answer 3

The e in an alkane becomes an “al”. Alkanals. The one which contains the aldehyde function, regardless of anything else. Numbering begins at the carbonyl carbon.

Question 4

When an aldehyde is attached to a ring, naming:

Answer 4

compound is a carbaldehyde, and the carbon atom with the -CHO group is carbon 1. The largest ring with the aldehyde function is the stem, regardless of other rings or chains. “Cyclohexanecarbaldehyde” or “benzaldehyde”

Question 5

Ketone naming

Answer 5

Ketones are alkanones (alkane –> alkanone), with the exception of propanone, which can be called acetone. Longest chain is the one with the C=O, and the carbonyl carbon is assigned the lower possible number in the chain, regardless of other substituents. Polyketones are
-diones, -triones, etc.

Question 6

Common names for HC=O and CH3C=O

Answer 6

Formyl for HC=O and acetyl for CH3C=O

Question 7

Common names for aldehydes

Answer 7

Simple aldehydes (like formaldehyde) are derived from the name of the corresponding carboxylic acid with the ending turned into an “aldehyde”

Question 8

Ranking of functional groups

Answer 8

Carboxylic acids over aldehydes over ketones, over everything else

Question 9

Solubility in water

Answer 9

Smaller carbonyl derivatives are miscible in water. More than 6 carbons and they get very not miscible, though.

Question 10

Carboxy group

Answer 10

A hydroxy unit attached to a carbonyl carbon, written COOH or CO2H

Question 11

Carboxylic acids naming

Answer 11

Alkanoic acids, except for methane and ethane. Methane –> formic acid (“from the destructive distillation of ants”), ethane –> acetic acid. The carboxy carbon must be in the stem, regardless of longest chain. It is given number 1, and other things are substituents. Takes precedence over ketones and aldehydes

Question 12

Acyl halide

Answer 12

RC=O X in which the X is a halide attached to the C

Question 13

Addition - elimination mechanism at Carboxy carbons

Answer 13

Carbonyl carbons are electrophilic, and can be attacked by nucleophiles. However, they’re sp2 hybridized and planar. planarity makes Sn2 difficult, but Sn1 is not favorable because they make bad carbocations. Thus, addition of the nucleophile occurs first (one step), then the elimination of the leaving group occurs (in a separate step!). The intermediate has tetrahedral structure, so it’s called a tetrahedral intermediate.

Question 14

Base catalyzed addition elimination

Answer 14

A nucleophile with a removable proton may be deprotonated by a strong base, making it even more nucleophilic. The leaving group ends up being negative, and can regenerate the base by stealing back the hydrogen, allowing the base to act as a catalyst. Often used with water or alcohol nucleophiles, which have strong conjugate bases

Question 15

Acid catalyzed addition elimination

Answer 15

1. Oxygen is protonated. Resonance means that the positive charge is shared between the oxygen and the carbonyl carbon, making the carbonyl carbon very electrophilic
2. Nucleophile adds to protonated C=O
3. Tetrahedral intermediate
4. Leaving group leaves
5. Deprotonation of the oxygen, regeneration of the catalytic proton.

Question 16

Does elimination - addition work for carboxylic acids?

Answer 16

It works best for their derivatives, in which the leaving group is something other than hydroxy. In Carboxylic acids, acid/base chem usually goes much more quickly than addition/elimination. However, it can work with weak nucleophiles.

Question 17

Acyl halide synthesis (from carboxylic acid)

Answer 17

Uses PBr3 or SOCl2, just like for alcohols –> haloalkanes. These transform the OH into a good leaving group. PBr3 turns it into OPBr2, while SOCl2 turns it into OSOCl. During both of these an H+ and the respective halide are generated, which come into play in subsequent steps of addition/elimination.

Question 18

Carboxylic anhydride

Answer 18

O O
|| ||
RCOCR

Question 19

Carboxylic anhydride synthesis

Answer 19

Acyl halide + carboxylic acid. Mechanism is typically carried out in the presence of a base, which first generates the carboxylate ion from an acyl halide (which is reactive because it activates the carbonyl). The mechanism then transverses the standard base-catalyzed addition/elimination sequence

Question 20

Synthesis of of cyclic anhydrides

Answer 20

Two ways:

1. Heating dicarboxylic acids so that they dehydrate and form a 5 or 6 membered ring (~300 C)
2. Thionyl chloride (SOCl2, 20 C)

Question 21

Ester

Answer 21

O
||
RCOR’

Question 22

Fischer esterification

Answer 22

O O
|| ||
RCOH + R’ OH —> RC OR’ + H2O
It’s not a super favorable reaction, so it’s usually achieved by using an excess of a small/cheap alcohol as a reagent + solvent.
1. protonation of the carboxy oxygen (resonance!)
2. attack my alcohol, and deprotonation (of alcohol) to give tetrahedral intermediate
3. protonation and elimination of water

Question 23

Ester hydrolysis

Answer 23

The opposite of Fischer esterification. It’s carried out under the same conditions as esterification, but with an excess of water to shift equilibrium to the other side.

Question 24

Hydride reduction of aldehydes and ketones

Answer 24

Using NaBH4 or LiAlH4, the addition of one H+ and one H- to the oxygen and carbon in the carbonyl results in an alcohol. The electrophilic H of NaBH4 attacks the carbonyl carbon, and switched some electron density to the oxygen, which is then protonated in a workup.

Question 25

Oxidation of an alcohol to a ketone or an aldehyde

Answer 25

Uses aqueous chromium VI, in the form of CrO3 or Na2Cr2O7, or (fav) pyridinium chlorochromate (PCC) which is used because it is not susceptible to overoxidation.

Question 26

Organometallic reagents

Answer 26

Nucleophilic carbon sources! Amazing. Created by the reaction between haloalkanes and magnesium or lithium. Grignard discovered the Mg ones. Grignard reagents are coordinated (attached ish) to the solvent, because they’re very electropositive and wouldn’t otherwise be stable.

Question 27

Addition of grignards to epoxides

Answer 27

The carbanion attacks at the least substituted carbon. Think about this if you see an oxygen two carbons away from one of your reagents in a synthesis problem. If the attack occurs at a secondary carbon, inversion will be observed

Question 28

Addition of grignards to aldehydes and ketones

Answer 28

Breaks the pi bond between the oxygen and the carbonyl carbon, forms a new sigma bond between the carbon of the grignard and the carbonyl carbon. Remember the workup to protonate the oxygen! Robak will be mad otherwise.

Question 29

Addition of grignards to esters

Answer 29

Esters consist of a carbonyl group directly attached to an OR group. When they react with grignards, two equivalents of carbanion get added. This happens when, instead of protonating the first oxygen to become negative (after the first pi bond is broken), the grignard steals it and completely breaks its bond to the C. Then the reaction continues as the second oxygen becomes a ketone and does the whole thing again.