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Flashcards in Carboxylic Acids Deck (98)
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1

What is the functional group of a carboxylic acid?

-COOH

2

How are carboxylic acids formed?

Oxidising primary alcohols under reflux

3

Which carboxylic acids are more soluble?

Why?

Those with a lower Mr

The -COOH forms hydrogen bonds with water

4

Why are carboxylic acids only weak acids?

They only slightly dissociate in water

5

How is a carboxylate ion formed?

The carbonyl group attracts e- away from the -OH group which leads to the -OH bond being weakened so a proton is easily lost

6

Why are alcohols not acidic?

The -OH bond does not easily break

7

How does adding a halogen to a carboxylic acid affect the pH?

Eg chloroethanoic acid

Chlorine atom is more electronegative so withdraws e- density away from the carbonyl carbon. This causes the O-H bond to become more polar and weaken.
More H+ is therefore released, decreasing the pH

8

What is more acidic: ethanoic acid or chloroethanoic acid

Why?

chloroethanoic acid

Cl pulls e- towards itself

9

How are acyl chlorides formed?

The -OH group of the carboxylic acid is replaced by a chlorine atom

10

Why is the carbon atom in acyl chlorides readily attacked by nucleophiles?

Cl and O are more electronegative than C so the C atom is delta positive

11

How are acyl chlorides named?

It is derived from their corresponding carboxylic acid

Eg ethanoic acid forms ethanoyl Chloride

12

When there is an -OH in the middle of a carbon chain, how can you refer to it in the name?

With ‘hydroxy’

13

How to form acid anhydrides from carboxylic acids?

-OH group is replaced by -OCOR

When two molecules of carboxylic acids join with the elimination of water

14

How do you name an acid anhydride?

The suffix -anhydride replaces the -acid suffix at the end of the carboxylic acid name

If the two C chains are different, write them in alphabetical order

15

What is a good leaving group?

A stable species removed during a chemical reaction

16

What is the leaving group of acyl chlorides?

What is the by product?

Cl-

HCl

17

What is the leaving group of an acid anhydride?

What is the by product?

-OCOR

The corresponding carboxylic acid

18

Name the mechanism and reaction name for acylation

Nucleophilic addition elimination

Reduction

19

Describe nucleophilic addition elimination

Nucleophile attacks the delta positive carbon of the carbonyl group forcing the e- to move from the carbonyl bond to the O making an oxyanion

Carbonyl bond remade causing elimination of the leaving group

Nucleophile loses a H+

20

How are carboxylic acids formed? (3)

1) primary alcohols or aldehydes oxidised by acidified potassium dichromate

2) acyl chlorides react with water (nucleophilic addition elimination)

3) acid anhydrides react with water

21

Test for carboxylic acids

What is formed?

Add Sodium carbonate and CO2 is evolved and fizzing is seen

Ionic salts - these are soluble in water

22

Name of reaction to form an Ester

What are the reactants?

What is the byproduct?

Esterification

Carboxylic acid + alcohol with concentrated H2SO4 (or another strong acid) as a catalyst

Water

23

What is the isomerism linking esters and carboxylic acids?

They are functional group isomers

24

How do you name an Ester?

The alkyl chain of the alcohol is the prefix

The second part of the name is derived from the carboxylic acid - -oic is replaced with -oate

25

What are the 3 ways to form an Ester?

Esterification
Acyl Chlorides reacting with alcohols
Acid anhydrides react with alcohols

26

What is the name for the formation of esters from acyl chlorides?

Nucleophilic addition elimination

27

What is esterification?

Mixing a carboxylic acid and an alcohol in the presence of a concentrated H2SO4 catalyst to form an Ester and water

28

What is a base added after the formation of an Ester from acyl chlorides?

To neutralise HCl

29

Why are acyl chlorides preferred to carboxylic acids in the formation of esters?

No acid catalyst required
Purer product
Yield of Ester is higher as acyl chloride reaction is not reversible

30

What is the mechanism to form an Ester from alcohols and acid anhydrides?

What is formed?

Nucleophilic addition elimination

An Ester and a carboxylic acid