carboxylic acids and esters

Question 1

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what functional group does a carboxylic acid contain

Answer 1

• carboxyl functional group

Question 2

what does the carboxyl group contain

Answer 2

• carbonyl group
• hydroxyl group

Question 3

what type of acid is a carboxylic acid

Answer 3

organic acid

Question 4

where are carboyxlic acid found

Answer 4

• medicines
• fruit juices
• vinegar
• rhubarb leaves

Question 5

wht are carboxylic acids and it’s derivatives used for

Answer 5

• used in organic synthesis as starting materials or intermediates in the formation of more useful compounds
• such as painkiller, aspirin, can be synthesised from salicyclic acid

Question 6

describe the solubility of carboyxlic acids

Answer 6

• C=O and O-H bonds in carboxylic acids are polar allowing carboxylic acids to form hydrogen bonds with water moleculess

Question 7

describe the solubility of carboxylic acid regarding the length of carbon chain

Answer 7

• carboxylic acids with up to four carbon atoms are soluble in water
• as the number of carbon atoms increases the solubility decreases as the non polar carbon chain has a greater effect on the overall polarity of the molecule

Question 8

describe solutbility of dicarboxylic acids

Answer 8

• two polar carboxyl groups to form hydrogen bonds
• solids at room temperature
• dissolve readily in water

Question 9

Describe the strength of carboxylic acids

Answer 9

• classified as weak acids
• when dissolved in water carboxylic acids partially dissociate

Question 10

Decribe acid reactions of carboxylic acids and wht they form

Answer 10

• redox and neutralisation reactions
• redox reactions with metals
• neutralisation reactions with bases (alkalis, metal oxides and carbonates)
• in reactions carboxlic acids from carboxylate salts

Question 11

how are carboxylate salts named

Answer 11

• named by changing the ic acid ending of the carboxylic acid to -ate

Question 12

describe redox reactions of carboxylic acids with metals

Answer 12

• aqueous solutions of carboxylic acids react with metal in a redox reaction to form hydrogen gas and a carboxylate salt
• observe metal dissappearing and effervesence as hydrogen gas is evolved

Question 13

describe the reaction of carboxylic acidswith metal oxides

Answer 13

• form a salt and water

Question 14

describe reactoion of carboxylic acids with alkalis

Answer 14

• form a salt and water
• may not see a reaction as two solutions react together to form an aquous solution of the salt

Question 15

describe reaction of carboxylic acids and carbonates

Answer 15

• carbon dioxide gas appear
• if carboxylic acids is in excess a solid carbonate would disappear

Question 16

How to test for the carboxyl group and wht do these distinguish between

Answer 16

• neutralisation reaction of carboxylic acids with carbonates
• carboxylic acid are only common organic compounds sufficiently acidic to react with carbonates
• used for distinguiishing carboxylic acids from phenols
• phenols are not acidic enough to react with carbonates

Question 17

what is a derivative of a carboxylic acid

Answer 17

• compound that can be hydrolysed to form a parent carboxylic acid
• carboxylic acid derivative have a common equence of atoms in their structure - acyl group

Question 18

name common derivative or carboxylic acids

Answer 18

• ester
• acyl chloride
• acid anhydride
• amide

Question 19

how is an ester named

Answer 19

• names after the parent carboxylic acids from which its derived
• to name the ester remove oic iffux from parent carboxylic acid and replace with oate
• alkyl chain attatched to oxygen atom of COO group is added as first word in the name
• eg ethanoic acid and methanol produce methl ethanoate and water

Question 20

how is an acyl chloride named

Answer 20

• named after the parent carboxylic acid ffrom which it is derived
• remove oic acid suffic from the parent carboxylic acid and replace with oyl chloride

Question 21

how is an acid anhydride formed

Answer 21

• removal of water from two carboxylic acid molecules

Question 22

what is esterification

Answer 22

• reaction of an alcohol with a carboxylic acid to form an ester and water
• alcohol is warmed with a carboxylic acid with a small amount of concentrated sulfuric acid acts as a catalyst

Question 23

what is the smell of esters

Answer 23

esters are sweet smelling liquids

Question 24

describe the hydrolysis of esters

Answer 24

• esters can be hydrolysed by aqueous acid or alklai

Question 25

what is hydrolysis

Answer 25

chemical breakdown of a compound in the prescence of water or in an aqueous solution

Question 26

what is acid hydrolysis of an ester

Answer 26

* acid hydrolysis of an ester is the reverse of esterification

Question 27

how do you carry out acid hydrolysis

Answer 27

* the ester is heated under reflux with dilute aqueous acid * ester is broken down by water with the acid acting as a catlyst

Question 28

what are the products of acid hydrolysis

Answer 28

* carvoxylic acid and an alcohol

Question 29

what is alkaline hydrolysis of an ester

Answer 29

* known a saponification * irreversible * ester heated under reflux with aqueous hydroxide ions

Question 30

what does alklaline hydrolysis of an ester produce

Answer 30

* a carboxylate ion and an alcohol

Question 31

describe the preparation of an acyl chlorides

Answer 31

* can be prepared directly from their parent carboxylic acid * by reaction with thionyl chloride SOCl2 * also produces SO2 and HCL evolved as gases leaving just the acyl chloride

Question 32

why should acyl chlorides be prepared in a fume cupboard

Answer 32

* products are harmful

Question 33

describe the reactivity of acyl chlorides

Answer 33

* acyl chlorides are very reactive and are very useful in organic synthesis * easily converted into carboxylic acid derviatives such a esters and amides with good yields * react with nuclophiles by losing the chloride ion whilst retaining the C=O double bond

Question 34

how are esters formed by acyl chloride

Answer 34

acyl chlorides react with alcohols to form esters

Question 35

describe the reaction of acyl chlorides with phenols and why carboxylic acids are not used

Answer 35

* form esters * carboxylic acids are not reactive enough to form esters with phenols * acyl chlorides and acid anhydrides are both much more reactive than carboxylic acid and react with phenols to produce phenyl esters * neither reaction needs an acid catalyst

Question 36

describe the reactants used to form phenol ethanoate

Answer 36

* ethanoyl chloride and phenol

Question 37

decribe the reaction of acyl chlorides with water

Answer 37

* when water is added to acyl chloride a violent reaction takes place with the evolution of dense steamy hydrogen chloride fumes * a carboxylic acid is formed

Question 38

describe the reaction of acyl chlorides with ammonia and amines

Answer 38

* ammonia and amines can act as nucleophiles by donating the lone pair of electrons on the nitrogen atom to an electron deficient species * the reaction with acyl chlorides form amides

Question 39

describe the reaction of ammonia with acyl chlorides

Answer 39

* forms primary amide

Question 40

what is a primary amide

Answer 40

nitrogen atom attatched to one carbon atom

Question 41

how many bonds can nitrogen make

Answer 41

* 3 bonds * 1 lone pair

Question 42

what is the reaction between primary amine and an acyl chloride

Answer 42

* same way as ammonia * form a seconday amide

Question 43

what is a secondary amide

Answer 43

* nitrogen atom is attatched to two carbon atoms

Question 44

describe the reactions that take place with acid anhydrides

Answer 44

* acid anyhdrides react in a similar way to acyl chlorides with alchols, phenols, water, ammonia and amines * less reactive than acyl chlorides and are more useful in some labratory preparations where acyl chloride may be too reactive

Question 45

what is produced when an anhydride reatcs with an alcohol

Answer 45

* forms a salt and a carboxylic acid