The keratin chains indicated by the diagram below have under

The -keratin chains indicated by the diagram below have undergone one chemical step. To alter the shape of the -keratin chains—as in hair waving—you will need to perform some subsequent steps. What would you do? Explain your reasoning. (Hint: you need a chemical step and shape remodeling step). Would you achieve the same result if you do the reactions in a different order? Explain. Also, provide the name of a chemical compound that can be used to promote the shown chemical reaction. Explain.

Solution

Ans.) The keratin chains indicated in the question should have undergone one chemical step (S-S to SH SH). To alter the shape of the keratin chains as in hair waving at first the shape remodeling is done and then chemical oxidation should be carried out.

In my opinion it is not achieved, if these reaction done in different order.

Hair is made up of a protein called keratin, which is also found in nails. In hair, keratin molecules are arranged in straight bundles. These bundles are held together by disulphide bonds (-S-S-) which give strength to the hair. These disulphide bonds are made up of amino acid called cysteine. The cysteine of one keratin molecule forms a disulphide bond with the cysteine of the adjecent keratin molecule. The more disulphide bonds present in a strand of hair, the straighter it is.

Hence, if you want straight hair then you need to use chemical which helps in formation of more disulphide bonds. While, for perms or curls, it is needed to break the disulphide bond. Ammonium thioglycolate is used for this purpose as it contains a thiol group (-SH). The thiol group replaces one of the sulphur atoms in the disulphide bond. When the disulphide bond is broken, the keratin bundles come apart and hair is weakened. Ammonium thioglycolate is therefore used widely in beauty parlours for hair re-styling.