organic chemistry

HideShow resource information

alcohols

mass spectrum - peak at 3230-3550

suffix-ol 

contains oh functional group

can be formed by fermintation

Conditions for fermentation 

* no oxygen as the reaction is anerobic

* yeast as a catalyst

* glucose(C6H1206)

* temperature of about 35-27 degrees is needed for enzymes to work

At low temperatures the reaction is slow at high temperatures the yeast dies so 35oc is a compromise temperature

Ethanol is produced

1 of 5

The difference between aldehydes and ketones

An aldyhyde has a hydrogen attached to c=o bond 

Ketones do not have this hydrogen 

A ketone must be attached to 2 carbohydrogen groups 

The presence of the hydrogen atom makes aldhydes very easy to oxidise. Aldhydes are very strong reducing agents 

Ketones are resistant to oxydation only very styrong oxidysing aggents such as potassium maganate solution can oxidise ketones

If an aldhyde is oxidisd under standard conditions a carboxylic acid will be formed 

if an aldhyde is oxidised under alkaline conditions a salt of carboxylic acid is formed

2 of 5

regents to oxidise ketones

Acidified pottasium dicromate

Small amount of pottasium dichromate is acidified  with dilute sulpuric acid (h2so4)

few drops of an aldhyde or ketone are added

if nothig happens the solution is warmed for a few minutes

Ketone - no change in the orange solution 

Aldhyde- solution turns from orange to green 

The orange dichromate ions have been reduced to green chronium ions by the aldhyde 

The aldyhyde is oxidysed to a a carboxylic acid 

Cr072-+ 14H+ +6e- = 2cr3+ +7H2O

RCHO+ H20= RCOOH + 2H+ + 2e-

The overall eqaution is 

3RCHO + Cr2O72- + 8h+ = 3RCOOH +2Cr3+ +4H2O

3 of 5

Fehlings solution/ Benedicts reagent

Fehlings and benidicts varients of the same thing.

Fehlings solution contains copper2 ions complexed with tartrate ions in a sodium hydroxide solution 

Complexing the tartrate iouns withy copper ions prevents the precipitation of copper hydroxide (Cu(Oh)2) 

Benidicts regent contains copper2 ions mixed with citrate ions in a sodium hydroxide solution (Na(Oh)) prevents the formation of a a copper carbonate precipitate

Both reagents used in the same way Aldyhyde or ketone added to solution 

Ketone_ no change in the blue solution 

Aldhyde_ The blue solution produces a solid red precipitate of copper-1-oxide

ALDHYDES REDUCE COMPLEXED COPPER2+ TO COPPER-1-OXIDE. BECAUSE THE ALDHYDE  IS OXYDISED IN A ALKALINE SOLUTION. A CARBOXYLIC SALT IS PRODUCED BY THE ALDHYDE

2cu+ in complex +OH- +2e- +cu2o + H2O

RCHO + 3Oh-= Rcoo- + 2h20 +2e-

The overall eqaution is 

RCHO + 2Cu2+ in complex +RCOO- + cu2o + 3H20

4 of 5

Tollens reagent

tollens reagent contains {Ag(NH3)2]

This is made from silver nitate solution (AgNo3)

add sodium hydroxide to silver nitrate to give a precipate of silver oxide

add dilute ammonia to disolve the solution

to carry out test add Aldyhide of ketonr to solution

Ketone_ No change in the colourless solution 

Aldehyde_the colourless solution pruduces a grey precipate of silver or a silver mirror on test tube

aldehydes reduce diammine silver ion to metalic silver .

. The solution is alkaline so a salt of carboxylic acid is produced

2Ag(NH3)2+ +e- = ag + 2Nh3

RCHO + 3OH- = RCOO- + 2H2O+ 2e-

The overall eqaution is 

2Ag(NH3)2++ RCO+3OH-=  2Ag +RCOO- +4Nh3 +2H2O

5 of 5

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Acids, bases and salts resources »