Carboxylic Acids

Question 1

Carboxylic acid

Answer 1

Contains both a carbonyl and hydroxyl group
Are always terminal groups
Most oxidized functional group with 3 bonds to oxygen

Question 2

Nomenclature for carboxylic acids

Answer 2

Will end in oic acid
Cyclic will end in oate
Dicarboxylic will end in suffix dioic acid

Question 3

Dicarboxylic acid

Answer 3

Has a carboxylic acid on each end of the molecules

Question 4

Physical properties of carboxylic acids

Answer 4

Hydrogen bonding from 2 oxygens - can form dimers- high melting and boiling points
Acidic primarily because of hydroxyl

Question 5

Describe the acidity of carboxylic acids

Answer 5

Comes from the hydroxyl. When it loses the proton the negative charge can be delocalized between the 2 oxygens and is stable - have resonance structures
More stable the conjugate base the easier it is for the proton to leave
Pka approx 4.8

Question 6

How can substituents on carbons near the carboxyl group affect acidity

Answer 6

Electron withdrawing groups like NO2 or halides increase acidity while electron donating groups like NH2 and OCH3 destabalize the negative charge decreasing the acidity
The closer the substituents are to the carboxyl group the greater the effect

Question 7

Describe the acidity of dicarboxylic acids

Answer 7

Each COOH will influence the other - they are electron withdrawing so will make more acidic for the first proton lost, but will be less acidic for the second proton because giving the molecule 2 negative charges would cause repulsion - second is less acidic than a normal carboxylic acid

Question 8

Beta dicarboxylic acid

Answer 8

Each carboxylic acid is positioned on the B carbon of the other carboxylic acid which makes the alpha hydrogens acidic pka 9-14 because of a stable carbanion due to electron withdrawing effects of both carboxyl groups

Question 9

How are carboxylic acids prepared

Answer 9

Oxidation of aldehydes and certain alcohols by potassium permanganate KMnO4
Secondary and tertiary alcohols cannot be oxidized to carboxylic acids because they already have at least 2 bonds to other carbons

Question 10

Describe nucleophilic acyl substitution

Answer 10

Opening up of the carbonyl via nucleophilic attack, forming a tetrahedral intermediate, the carbonyl reforms and the leaving group is kicked off
*replaces leaving group with acyl derivative

Question 11

What are acyl derivatives

Answer 11

All molecules with a carboxylic acid derived carbonyl including carboxylic acids, amides, esters, and anhydrides

Question 12

What conditions favour a nucleophilic acyl substitution

Answer 12

A good leaving group, wake bases make good leaving groups

Basic or acidic conditions

Question 13

Amides

Answer 13

Formed from carboxylic acids when the incoming nucleophile is ammonia or an amine
Can be carrried out in either acidic or basic conditions
End in amide and alkyl groups on N are places at beginning after N
Exist in a resonance state with delocalization between oxygen and nitrogen

Question 14

Lactam

Answer 14

Cyclic amide - end with lactam and may be named for the specific carbon that is bound during cyclization eg b lactam or y lactam

Question 15

Ester

Answer 15

Hybrid between a carboxylic acid and an ether which can be made by reacting carboxylic acids with alcohols under acidic conditions

Question 16

Esterification

Answer 16

A condensation reaction with the release of water
In acidic environments the carboxyl oxygen will be protonated which will enhance the polarity and increase susceptibility to nucleophilic attack
Condensation reaction occur more rapidly with primary alcohols

Question 17

Lactone

Answer 17

Cyclic ester - named with suffix lactone

Question 18

Anhydride

Answer 18

Formed from the condensation of two carboxylic acids have a nucleophilic acyl substitution
When naming replace acid with anhydride whether linear or cyclic

Question 19

Reduction of carboxylic acids

Answer 19

Can be reduced to primary alcohols but lithium aluminum hydride but but not sodium borohydride

Question 20

Decarboxylation

Answer 20

The complete loss of a carbonyl group as carbon dioxide

Question 21

Describe the process of decarboxylation.

Answer 21

1,3 dicarboxylic acids and other beta ketoacids may spontaneously decarboxylate when heated - carboxyl group is lost and replace with a hydrogen
Both electrophile and nucleophile are in same molecule so form 6 membered cyclic transition state
Enol that forms from the destruction of the ring tautomerizes to keto form

Question 22

Saponification

Answer 22

Mixing fatty. Acids with lye (sodium or potassium hydroxide) resulting the formation of a salt we call soap

Question 23

Soap

Answer 23

Can solvate non-polar organic compounds in aqueous solution because contain non-polar tail and polar carboxylate

Question 24

Michelle

Answer 24

When soap is placed in aqueous solution polar heads face outward and non polar tails face inwards forming a sphere - non polar substances can be dissolve inside