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The question is to make Sec-butyl Bromide from alcohol. From what i have read, 2° and 3° alkyl bromide and alkyl iodide cannot be formed with Conc H2SO4 as it will make it into alkene.

I have tried P4 + 6Br2 = 4PBr3 But-2-ol + PBr3 = 3 2-bromo butane + H3PO3

Is there any other way?

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A good way is to form a sulfonate of the alcohol (tosylate, mesylate, triflate etc) forming a good leaving group then react that with a source of bromide anion.

The standard way of forming a tosylate is with p-toluenesulfonyl chloride in the presence of a base, pyridine catalyses the reaction so is often used as the base. There are many ways to react the tosylate with a source of bromide. I prefer using phase-transfer catalysis in dichloromethane/aqeous potassium bromide with tetrabutylammonium bromide catalysis, this works for mesylates too.

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