The highly alkaline chemical agent which is most commonly used in the formulation of cosmetic depilatories to chemically break the strong disulfide (−S−S−) bonds of hair keratin is
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Depilatories are cosmetic products that remove unwanted hair by chemically dissolving it. Hair is made of keratin, a tough protein held together largely by disulfide (−S−S−) bonds.
Step 1: What are depilatories? Depilatories are chemical agents applied to skin to remove unwanted hair. They work by breaking the structural bonds of hair.
Step 2: Hair structure and disulfide bonds. Hair is made of keratin protein. Keratin chains are held together by strong disulfide bonds (-S-S-) between cysteine residues. Breaking these bonds destroys the hair structure.
Step 3: Why thioglycolate? Calcium thioglycolate is a reducing agent. It donates electrons to break the -S-S- disulfide bond into two -SH (thiol) groups, completely disrupting the hair's mechanical strength. The hair then dissolves or can be wiped away easily.
Step 4: Why highly alkaline? Alkaline pH (around 10-12) speeds up the thioglycolate reaction and helps swell the hair shaft, improving penetration.
Step 5: Rule out distractors. Hydrogen peroxide is an oxidizing bleach, not a depilatory. Sodium lauryl sulfate is a detergent/surfactant. Aluminum chlorohydrate is an antiperspirant. None of these break disulfide bonds like thioglycolate does.