carboxylic acids and derivatives

Question 1

carboxylic acids are weak acids. meaning

Answer 1

they slightly dissociate/ionise when in solution

Question 2

how can you test for them

Answer 2

react with carbonates. forms CO2 as a gas and can bubble through limewater to confirm its presence.

the reaction observes fizzing and bubbling

–
any reaction with c acid I’d slower because they are weak acids so barely donate protons

Question 3

why can they form H bonds with water

Answer 3

they have O-H bonds. difference in electronegativity and the high mass to charge ratio of H gives it a strong delta positive charge

the lone pair of electrons on the O in H2O is attracted to it forming H bonds, due to imf

Question 4

reaction for ester formation

conditions

Answer 4

esterification
// is a reversible reaction:
acid + alcohol <=> ester + water

// conditions: conc H2SO4 (strong acid catalyst), under reflux

very slow reaction

Question 5

how do you name an ester

Answer 5

__yl __oate

-yl part derived from alcohol (how many Cs on the C-O side of the COO f group)
-oate part derived from c acid (how many Cs on the C=O side of the COO f group)

Question 6

how is an ester formed

Answer 6

the -OH from the avid and H from the alcohol react to form water

Question 7

f group of esters

Answer 7

RCOOR

O
||
R-C-O-R

Question 8

uses of esters

Answer 8

used in food flavourings and perfumes because they are sweet smelling compounds

they have low BPs and make good solvents for other polar molecules

used in plasticisers (substance added to material to make it more flexible)

Question 9

uses of esters

Answer 9

used in food flavourings and perfumes because they are sweet smelling compounds

they have low BPs and make good solvents for other polar molecules

used in plasticisers (substance added to material to make it more flexible) to increases elasticity and softness of materials.

Question 10

[[ where else in the course do we encounter plasticisers ]]

Answer 10

used to make rigid pvc (addition polymer (long chain molecule), alkene) more flexible. there are strong imfs between pvc molecule chains because large Mr means many electrons so strong VdWs, but plasticiser disrupts the layers weakening the IMFs

plasticised pvc is used for cablewirr insulation, clothing (waterproof and sport)

Question 11

fats and oils are

how are they formed

Answer 11

triglycerides, a type of lipid. these are esters because they are formed by the reaction between glycerol (propane123triol) and 3 fatty acids of variable chain length

Question 12

why are fats solid and oils liquid

Answer 12

fats tend to have saturated fatty acid chains so chain is linear. so stronger IMFs

oils tend to have unsaturated fatty acid chains so chain is bended, but bends only occur if Z isomerism. so weaker IMFs

Question 13

glycerol undergoes esterification to form

Answer 13

triglyceride esters

the H on all of its OH groups and the OH from the COOH group of three fatty acids react to form triglyceride esters AND don’t forget 3 waters

Question 14

in what two ways can esters be hydrolysed

Answer 14

hydrolysis in acidic conditions to form an alcohol and a carboxylic acid (reverse of esterification) by adding water. is a reversible reaction so will shift to reactants side to decrease conc water, increasing yeild of reactants, thereby hydrolysing the ester

hydrolysis in alkaline conditions to form soap, known as saponification

Question 15

ester hydrolysis in acidic conditions

Answer 15

strong acid catalyst is needed for this reversible reaction

simple reverse reaction, the backwards reaction to an alcohol and c acid

Question 16

hydrolysis of esters in alkaline conditions:
- what happens
- conditions
- use

Answer 16

WHAT HAPPENS
ester and NaOH in aqueous solution (ratio 1:3) will react to form salt of fatty acids and glycerol.

the triglyceride is hydrolysed to form glycerol and fatty acid chains which have COO- f group carboxylate instead of COOH. this reacts with the Na+ or whatever cation to form 3 salts of the fatty acid as well as the glycerol

triglyceride+ 3NaOH -> 3salts of fatty acid and glycerol (OH- bonds with glycerol that doesn’t have any of its OH groups)

CONDITIONS
boiled with metal hydroxide as reagent

USE
the fatty acid salts are used as soaps because they have hydrophilic and hydrophobic properties

Question 17

as well as soap, triglycerides can produce biodiesel

what is biodiesel

Answer 17

renewable biofuel derived from biological sources like vegetable oils, animal fats or recycled greases

it is a mixture of methyl esters of long chain carboxylic acids

Question 18

reaction to form biodiesel

Answer 18

1. lipid is broken down into 3 fatty acids and glycerol by reaction with KOH
2. these fatty acids are converted into three new ester using methanol. methanol reacts with fatty acids to form methyl (__oate (depends on formula of long chain fatty acids)) esters.
3. overall the KOH is not used up and so acts as a catalyst

Question 19

how could biodiesel potentially be a carbon neutral fuel

why is it’s production kinda bad

Answer 19

no net release of carbon dioxide to the atmosphere because the same amount of CO2 released when the fuel is burned is absorbed from the crops it was made from during photosynthesis

its production uses a lot of farmland instead of using it for food production

Question 20

+ acylation