esters, fats and oils

Question 1

what is an ester?

Answer 1

a molecule containing an ester link- —COO—

Question 2

how are esters made?

Answer 2

from the condensation reaction between a carboxylic acid and an alcohol

Question 3

what is a condensation reaction?

Answer 3

a reaction in which molecules join with the elimination of a small molecule (often water)

Question 4

what is the other name for condensation of a carboxylic acid and an alcohol?

Answer 4

esterification

Question 5

what happens during esterification?

Answer 5

1. the H atom of the hydroxyl group and the OH of the carboxyl group break off to form a water molecule.
2. the alcohol and acid molecules join to form the ester link (carboxylate group)

Question 6

how do you name an ester?

Answer 6

first name- alcohol molecule (e.g, methyl)
second name- carboxylic acid (e.g, propanoate.)

Question 7

how to recognise the acid part of the ester?

Answer 7

the double o will be bonded here.
in terms of formula- the acid will have a ‘line’ carbon not bonded to any h’s

Question 8

what are esters commonly used as?

Answer 8

flavourings and fragrances- commonly having pleasant, fruity smells. they are also a good non polar solvent for varnishes paints and adhesives that do not dissolve in water.

Question 9

what is hydrolysis ?

Answer 9

the break down of a compound using the chemical action of water

Question 10

esters can be hydrolysed to produce….

Answer 10

an alcohol and a carboxylic acid

Question 11

a hydrolysis reaction is the reverse of a…

Answer 11

condensation reaction

Question 12

for complete hydrolysis of an ester, what is required?

Answer 12

a strong alkali and heating under reflux (alkaline hydrolysis)

Question 13

what is the percentage yield equation ?

Answer 13

actual yield
—————- x 100
theoretical yield

Question 14

how to find the percentage yield ?

Answer 14

1. find the number of moles of one substance
2. apply that to the mole ratio of the other substance to find out how many moles of said other substance are required
3. do m=nxg equation using that ^^^ to find the theoretical yield, then do the actual yield over that x 100.

Question 15

what are edible fats and oils/how are they formed?

Answer 15

esters formed from the condensation of glycerol (propane1-2-3-triol) and three carboxylic acids. the carboxylic acids are known as fatty acids which have long chains of carbon atoms

Question 16

how to find out if a fatty acid is saturated using the molecular formula ?

Answer 16

take away COOH functional group and one CH3. if the remaining formula is equal to cnh2n then it is saturated. anything less is unsaturated.

Question 17

how to tell degree of saturation in a fatty acid/oil?

Answer 17

decolourising bromine test

Question 18

why are fats and oils important in our diet ?

Answer 18

1. they are a concentrated source of energy
2. they are essential for thr transport and storage of fat soluable vitamins in the body.

Question 19

describe why fats and oils have different mp/bp.

Answer 19

edible oils have lower melting points than edible fats. this is because saturated fatty acids always give linear structures which allows the chains to pack closely together allowing for maximum van der waals forces to occur resulting in higher mp. unsaturated fatty acids (oils) are bent at the double c-c double bond meaning the molecules are unable to pack closely together therefor maximum van der waals forces cannot be obtained.

Question 20

what is ‘hardening’ an oil?

Answer 20

the process of hydrogenating a fat or oil to increase its melting point by adding hydrogen. (addition reaction)