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THEORY Electrophilic addition is the most characteristic reaction of A variety o

ID: 534045 • Letter: T

Question

THEORY Electrophilic addition is the most characteristic reaction of A variety of electrophiles X-Y) will add across the double bond of an alkene to yield a saturated compound. If bromine (Br) is the electrophile, the resulting compound is a 1,2-dibromide (also called a vicinal dibromide) (2). I Y CEC X-Y (1) C C Br-Br Br 1,2-dibromide (vicinal dibromide) Typically, brominations of alkenes are carried out in methylene chloride (CH2Cl2 or carbon tetrachloride solvents are ideal because they are non-reactive and will not interfere with the desired reaction. However, both solvents are volatile and toxic and both are suspected The traditional reagen used for these brominations, Br2, is also to handle because it is highly corrosive and causes severe burns upon contact with the skin. In this experiment, you will brominate (E) stilbene using alternative reaction conditions: pyridinium tribromide in ethanol (EtOH) 3).

Explanation / Answer

To make it safer and greener you can make following changes which is usually practiced in many
green Ochem labs,
1) Substitute solvents like CH2Cl2 and CCl4 with alcohols
2) Instead of using Br directly you can use Pyridinium tri-bromide which in turn breaks down itself
   to give bromine indirectly and slowly which is safer.
    C5H6Br3N  ---------------> C5H6BrN + Br2