carboxylic acids and derivatives

Question 1

carboxylic acids solubility in water and trend

Answer 1

The smaller carboxylic (up to C4)
acids dissolve in water in all
proportions but after this the solubility
rapidly reduces. They dissolve
because they can hydrogen bond to
the water molecules.

Question 2

acidity of carboxylic acids

Answer 2

The carboxylic acid are only weak acids
in water and only slightly dissociate, but
they are strong enough to displace
carbon dioxide from carbonates.

Question 3

trend in strength of carboxylic acids

Answer 3

Increasing chain length pushes
electron density on to the COOion, making it more negative and
less stable. This make the acid
less strong.

Question 4

what atom makes a carboxylic acid stronger and why

Answer 4

chlorine - Electronegative chlorine atoms
withdraw electron density from
the COOion, making it less
negative and more stable. This
make the acid more strong.

Question 5

Salt formation reactions of carboxylic acids

Answer 5

acid + metal (Na) = salt + hydrogen
2CH3COOH + 2Na = 2CH3COO- Na+ + H2

acid + alkali (NaOH) = salt + water
CH3COOH + NaOH = CH3COO- Na+ + H2O

acid + carbonate (Na2CO3) = salt + water + CO2
2CH3COOH + Na2CO3 = 2CH3COO- Na+ + H2O + CO2

Question 6

how to test for carboxylic acids

Answer 6

The effervescence caused by the production of CO2
with carboxylic acids with solid Na2CO3 or
aqueous NaHCO3 can be used as a functional
group test for carboxylic acids

Question 7

which carboxylic acid is an exception and CAN be oxidised

Answer 7

methanoic acid - Carboxylic acids cannot be oxidised by using
oxidising agents but methanoic acid is an
exception as its structure has effectively an
aldehyde group

Question 8

esterification reaction and conditions

Answer 8

carboxylic acid + alcohol = ester + water

heating under reflux and H2SO4 catalyst

Question 9

what type of reaction is esterification

Answer 9

reversible

Question 10

naming esters

Answer 10

The bit ending in –yl comes from
the alcohol that has formed it
and is next to the single bonded
oxygen.

The bit ending in –anoate
comes from the carboxylic
acid and includes the C in
the C=O bond

Question 11

esterification reaction equation for ethanoic acid and ethanol

Answer 11

CH3COOH + CH3CH2OH =(reversible)= CH3COOCH2CH3 + H2O

Question 12

uses of esters

Answer 12

perfumes, flavourings

Question 13

how to reverse esterification reagents conditions and reaction name

Answer 13

hydrolysis,

dilute HCl, heat under reflux

Question 14

other reaction to reverse esterification reagents conditions etc

Answer 14

hydrolysis with dilute sodium hydroxide

heat under reflux

Question 15

problem with acid hydrolysis of esters

Answer 15

reversible so doesnt give a good yield

Question 16

why is hydrolysis with NaOH not reversible

Answer 16

carboxylic acid salt produced is an anion, resistant to attack from nucleophiles such as alcohols so not reversible

Question 17

what is formed when you hydrolise fats and vegetable oils

Answer 17

propane-123-triol (glycerol)

long chain carboxylic (fatty) acids

Question 18

uses of glycerol and why

Answer 18

used in cosmetics, food and glues as it can hydrogen bond so is soluble in water

Question 19

use of long chain fatty acids and why

Answer 19

soap
polar COO- end is hydrophilic and mixes with water
non-polar hydrocarbon end is hydrophobic and mixes with grease
this enables grease and water to mix

Question 20

how to make biodiesel reagent and conditions

Answer 20

react vegetable oil/fat with methanol in the presence of a strong alkali catalyst

Question 21

are acyl chlorides more reactive than carbox acids and why

Answer 21

yes, because Cl and -OCOCH3 are good leaving groups

Question 22

reaction of acyl chloride with water info

Answer 22

forms carboxylic acid and produces steamy white HCl fumes (mostly gives HCl fumes not carbox acid)
room temp, water

Question 23

general equation for acyl chloride + water

Answer 23

RCOCl + H2O = RCOOH + HCl

Question 24

what mechanism do acyl chlorides and acid anhydrides do

Answer 24

nucleophilic addition-elimination

Question 25

acid anhydride + water reaction info

Answer 25

forms carboxylic acid

room temp water

Question 26

acid anhydride + water general equation

Answer 26

(RCO)2O + H2O = 2RCOOH

Question 27

acyl chloride + alcohol reaction info

Answer 27

forms ester
room temp alcohol
steamy white fumes of HCl given off

Question 28

why is acyl chloride + alcohol better for making esters than with carboxylic acids

Answer 28

faster, not reversible

Question 29

general equation for acyl chloride + alcohol (ethanol)

Answer 29

RCOCl + CH3CH2OH = RCOOCH2CH3 + HCl

Question 30

acid anhydride + alcohol reaction info

Answer 30

forms ester and carboxylic acid

room temp alcohol

Question 31

general equation for acid anhydride + alcohol (ethanol)

Answer 31

(RCO)2O + CH3CH2OH = RCO2CH2CH3 + RCOOH

Question 32

acyl chloride + ammonia reaction info

Answer 32

forms primary amide and NH4CL gas (white smoke)

room temp ammonia

Question 33

general equation for acid anhydride + ammonia

Answer 33

RCOCl + 2NH3 = RCONH2 + NH4Cl

Question 34

acid anhydride + ammonia reaction info

Answer 34

forms primary amide and ammonium salt

room temp ammonia

Question 35

acid anhydride + ammonia general equation

Answer 35

(RCO)2O + 2NH3 = RCONH2 + RCOO-NH4+

Question 36

acyl chloride + primary amine reaction info

Answer 36

forms secondary amide

room temp primary amine

Question 37

general equation for acyl chloride + primary amine using CH3NH2

Answer 37

RCOCl + 2CH3NH2 = RCONHCH3 + CH3NH3+Cl-

Question 38

acid anhydride + primary amine reaction info

Answer 38

forms secondary amide

room temp primary amine

Question 39

general equation for acid anhydride + primary amine using CH3NH2

Answer 39

(RCO)2O + 2CH3NH2 = RCONHCH3 + RCOO-CH3NH3+