C26 Carbonyls And Carboxylic Acids

Question 1

What’s the carbonyl group

Answer 1

C=O

Question 2

How do you name aldehydes

Answer 2

-al suffix (C=O is on the end of a chain)

Question 3

How do you name ketones

Answer 3

-one stuffix (designate number for which carbon C=O is on)

Question 4

What kind of intermolecular forces do molecules with the carbonyl group have? Why?

Answer 4

Permanent dipole-dipole

due to polar C=O bond

Question 5

How soluble are they in water? What influences solubility?

Answer 5

Form HBs between H2O molecules and O of C=O

As C chain length increases, solubility decreases

Question 6

Which bond in carbonyl compounds is usually involved in reactions? Why?

Answer 6

C=O

due to polarity of bond (large difference in EN between C and O)

Question 7

What’s the strongest bond in carbonyl compounds

Answer 7

C=O

Question 8

Why’s the addition of HCN important

Answer 8

Increases length of carbon chain by 1 C atom

allowing more useful molecules to be made

Question 9

Will the product of HCN added to a carbonyl compound have optical isomers? Why?

Answer 9

Yes

In aldehyde/ketone, carbonyl C is planar, so :CN^- can attack from either above or below, forming 2 enantiomers

Question 10

What’s the name of the product when HCN is added to a carbonyl compound

Answer 10

Hydroxynitrile (have OH and CN groups)

Question 11

What’s Fehling’s solution? What’s Colour is it?

Answer 11

Copper complex ions, blue

Question 12

What happens when an aldehyde is added to Fehling’s solution

Answer 12

Reduced to Cu^+ ions —> colour change to brick red ppt

Question 13

What happens when a ketone is added to Fehling’s solution

Answer 13

No visible change —> stays blue

Question 14

How do you test for a carbonyl compound

Answer 14

Brady’s reagent - 2,4-DNP

carbonyl compound present =
orange ppt formed

Question 15

What’s is in tollens’ reagent

Answer 15

Silver complex ions in colourless solution

Question 16

What happens when an aldehyde is added to Tollen’s reagent

Answer 16

Silver mirror forms as Ag+ reduced to Ag(s)

Question 17

What happens when a ketone is added to tollen’s reagent

Answer 17

No visible change

Question 18

What’s another oxidising agent for alcohols and aldehydes? What change in colour does this undergo?

Answer 18

Acidified potassium dichromate (VI) - H2SO4 and K2Cr2O7

Colour change from orange to green

Question 19

What’s a reducing agent for aldehydes and ketones? What ions does this release in solution?

Answer 19

NaBH4 [sodium tetrahydridoborate (III)] releases an H- ion

Question 20

How do you convert an aldehyde to form a carboxylic acid

Answer 20

Oxidation of aldehydes using Cr2O7^2-/H+ (i.e. K2Cr2O7/H2SO4)

Question 21

Are carboxylic acids soluble in water? Why? What influences their solubility?

Answer 21

Yes

Acid group can form hydrogen bonds with water molecules

Question 22

What are the IMF’s in carboxylic acids

Answer 22

Hydrogen bonds in solid state - very strong

Question 23

What are esters (what are they formed from)? Functional group, general formula?

Answer 23

Formed from carboxylic acids and alcohols.

RCOOR’ (C=O, C-O-C)

Question 24

How do you name esters?

Answer 24

Start with the alcohol group that has replaces the hydrogen, the acid part e.g. propyl (from alcohol) ethanoate (from carboxylic acid)

Question 25

What characteristic physical properties do esters have

Answer 25

Volatile, pleasant fruity smells e.g. apple, pear drops

Question 26

What are some uses of esters

Answer 26

Flavourings perfumes (both for longer chains) solvents (short chains) plasticisers.

Question 27

How could you distinguish carboxylic acids from other -OH containing compounds?

Answer 27

Add NaHCO3, acids will produce sodium salt, water and carbon dioxide

Question 28

What catalyst is needed for the formation of esters from alcohols and carboxylic acids

Answer 28

Concentrated strong acid e.g. H2SO4

Question 29

What catalyst is needed for the hydrolysis of esters

Answer 29

Dilute strong acid e.g. H2SO4

Question 30

What’s an alternative method of hydrolysis

Answer 30

Base hydrolysis

Question 31

What are the advantages of base hydrolysis

Answer 31

Reaction goes to completion due to neutralisation by base - more product in the mixture than acid catalysed hydrolysis

Question 32

What are carboxylic acid derivatives

Answer 32

Molecules that have the acyl group as part of their structure, formed from carboxylic acids

Question 33

Name 2 acid derivatives and give their functional groups

Answer 33

Acyl chlorides: RCOCl Acid anhydrides: RCOOCR/(RCO)2O

Question 34

How do you form an acyl chloride

Answer 34

React a carboxylic acids with SOCl2

Question 35

If the nucleophile is ammonia for the acylation of acyl chlorides or acid anhydrides, what are the products of the reaction

Answer 35

An amide

Question 36

If the nucleophile is a primary amine, what are the products of the acylation of acyl chlorides or acid anhydrides

Answer 36

N-substituted amide

Question 37

If the nucleophile is an alcohol, what are the products of the acylation of acyl chlorides or acid anhydrides

Answer 37

An ester

Question 38

If the nucleophile is water, what are the products of the acylation of acyl chlorides or acid anhydrides

Answer 38

Carboxylic acid (hydrolysis produces an ester linkage)

Question 39

What’s the name of the acylation of acyl chlorides/acid anhydrides with water as a nucleophile?

Answer 39

Hydrolysis