carboxylic acids and derivatives

Question 1

what is a carboxylic acid

Answer 1

COOH

Question 2

how do you name carboxylic acids

Answer 2

-oic acid

Question 3

are they soluble in water

Answer 3

yes, acid group can form hydrogen bonds with water molecules

Question 4

what intermolecular forces in carboxylic acids

Answer 4

hydrogen bonds in solid state

Question 5

what are esters

Answer 5

formed from carboxylic acids and alcohols

RCOOR’

Question 6

naming esters

Answer 6

start with the group that has replaced the hydrogen the acid part

Question 7

what physical properties do esters have

Answer 7

volatile, pleasant fruit smells

Question 8

uses of esters

Answer 8

flavourings,
perfumes
solvents
plasticisers

Question 9

common natural esters

Answer 9

fats

oils

Question 10

how could you distinguish carboxylic acids from other OH containing compounds

Answer 10

NaHCO3

acids will produce sodium salt water and carbon dioxide

Question 11

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

Answer 11

concentrated strong acids

H2SO4

Question 12

what catalyst is needed for the hydrolysis of esters

Answer 12

dilute strong acid

H2SO4

Question 13

what is an alternative method of hydrolysis

Answer 13

base hydrolysis

Question 14

what are the advantages of base hydrolysis

Answer 14

reaction goes to completion due to neutralisation by base

more product in the mixture than acid catalyst hydrolysis

Question 15

what is the difference between oil and fat

Answer 15

oils are liquid at room temp

fats are solid that are usually saturated

Question 16

how do you make biodiesel

Answer 16

NaOH catalyst

lipids + 3CH3Oh -> 3 methyl esters + glycerol

Question 17

what does transesterification mean

Answer 17

converting one type of ester to another

Question 18

how is the reaction mixture of biodiesel purified and separated

Answer 18

settling tank or centrifuge- remove remainder with water
add acid to neutralise excess alkali catalyst
solid soap is formed

Question 19

what is the problem with producing biodiesel

Answer 19

crops that could be used to make food are being used to make fuel

Question 20

what are carboxylic acid derivatives

Answer 20

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

Question 21

name two acid derivatives and give their functional groups

Answer 21

acyl chlorides RCOCL

acid anhydrides RCOOCR

Question 22

which factors determine how readily the acylation of a nucleophile by an acid derivative occurs

Answer 22

magnitude of the delta + charge on the carbonyl carbon
how easily the atom being substituted is lost
how good the nucleophile is

Question 23

what effect does the Cl and O in AC\AA have on the partial charge of the carbonyl carbon

Answer 23

increases the partial + charge by attracting electrons, this means that they react more readily with nucleophiles

Question 24

are more AC or AA more reactive

Answer 24

AC

Question 25

what is the name of the mechanism by which Ac and AA nucleophiles

Answer 25

addition-elimination

Question 26

if the nucleophile is ammonia for the acylation of AC or AA what are the products

Answer 26

an amide

Question 27

if the nucleophile is a primary amine, what are the products of the acylation of AC or AA

Answer 27

N-substituted amide

Question 28

if the nucleophile is an alcohol, what are the products of the acylation of Ac or AA

Answer 28

ester

Question 29

if the nucleophile is water, what are the products of the acylation of AC or AA

Answer 29

carboxylic acid

Question 30

what is a commercially important acylation reaction

Answer 30

manufacture of asprin

Question 31

what are the advantages of using ethanoic anhydride as an acylating agent over ethanoyl chloride

Answer 31

cheaper, less corrosive, does not react readily with water, safer

Question 32

what would you observe in a melting point determination if the sample was not pure

Answer 32

sample melts over a large range

sample’s melting point is below the accepted value

Question 33

why might the melting point appear different to the true value

Answer 33

temperature of the material in the machine might be different to the temperature shown on the thermometer

Question 34

when removing flue gases what are the issues

Answer 34

disposal of large amounts of CaSO3 and CO2 is produced

Question 35

what conditions are needed to form methyl esters from an AA or AC

Answer 35

methanol

heat gently under reflux

Question 36

when purifying by recrystallisation why is the minimum volume of hot solvent used

Answer 36

so that a saturated solution is created so that as many crystals will fall out of solution as possible when cooled

Question 37

why is the solution filtered hot when purifying by recrystallisation

Answer 37

to remove insoluble impurities and ensure that the crystals do not form in the filter paper

Question 38

why is the solution cooled in an ice bath when purifying by recrystallisation

Answer 38

to ensure that as many crystals as possible fall out of solution

Question 39

how would you separate the crystals from the reaction mixture when purifying by recrystallisation

Answer 39

filter under reduced pressure using a Buchner funnel