esters use (1 Viewer)

[clever angel]

hi ppl

help needed on this dotpt:

describe the uses of esters as flavours and perfumes in processed foods and cosmetics

also

outline the occurrence, production and uses of esters--i get the uses but not the occurrence bit?

thanks heapssss

 

[rnitya_25]

outline the occurrence, production and uses of esters--i get the uses but not the occurrence bit?

its all in the maq guide. if you really want me to type it up, i will.

 

[Dreamerish*~]

• Describe the uses of esters as flavours and perfumes in processed foods and cosmetics

This answers itself. If you want to go further, give an example - ethyl butanoate is used for strawberry flavours.

• Outline the occurrence, production and uses of esters

Esters have pleasant, fruity odours and occur widely in nature as perfumes and flavouring agents. While the characteristic smells or flavours of many plants and fruits usually arise from a complex mixture of substances, often one ester can be identified as the major ingredient of the smell or flavour.

There is now a substantial industry for developing and manufacturing synthetic flavours and perfumes. The first step is often to identify the constituents of the natural flavour and then to synthesise similar mixtures of esters which reproduce this flavour. Such artificial flavours are often cheaper than natural extracts.

Esters are made from alkanoic acids which react with alcohols. This reaction is acid-catalysed (generally concentrated sulfuric acid).

• The alkanoic acid and alcohol are placed inside a round bottomed flask, which is immersed in a water bath (beaker filled with water) - this is to prevent direct contact between the flask and the flame, as the reactants are volatile.
• Boiling chips are added to ensure uniform heat distribution and even boiling.
• Concentrated sulfuric acid (H₂SO₄) is used as a catalyst which not only reduces the activation energy, but increases yield by absorbing water. Because water is a product of the esterification reaction, removing it as it forms shifts the equilibrium to the right.
• Refluxing apparatus is used so that the process can be carried out at high temperatures. When the volatile reactants are heated to a high temperature, they become gases are may escape from the flask. Blocking the neck of the flask is dangerous, therefore refluxing apparatus is used to prevent the volatile reactants from escaping. Cool water is flown into the condenser from the bottom and out from the top. As the volatile reactants enter the condenser they cool, condense and trickle back into the reaction flask.

Uses have already been discussed.

Here is an example of an esterification reaction - the sulfuric acid actually takes part in the reaction, but we don't have to include it in the equations.

CH₃COOH_(aq) + CH₃OH_(aq) H₂SO₄ > CH₃COOCH_3(aq) + H₂O_2(l)

That's not much use because it doesn't show the structural formulae. Have a look at your textbooks and you should find diagrams of the refluxing apparatus and structural formulae of both reactants and products.

 

[rnitya_25]

thanks for saving me from typing all that up.

 

[Dreamerish*~]

thanks for saving me from typing all that up.

Haha, no worries. I needed revision in that module anyway.