Question

The addition of bromine​ to trans but $ - 2 - $ ene produces :
(A) Meso $ - 2,3 - $ dibromo butane
(B) $ \left( + \right) - 2,3 - $ dibromo butane
(C) $ \left( - \right) - 2,3 - $ dibromo butane
(D) None of the above

Answer 1

Hint :Bromine is an atomic number $ 35 $ chemical element with the symbol $ Br $ . It is the third-lightest halogen, and at room temperature, it's a fuming red-brown substance that quickly evaporates to become a similar-coloured gas.

Complete Step By Step Answer:
$ 2 - $ Butene, also known as but $ - 2 - $ ene, is a four carbon acyclic alkene. That's the most basic alkene with cis/trans isomerism, meaning it has two geometric isomers: cis $ - 2 - $ butene and trans $ - 2 - $ butene.
meso $ - 2,3 - $ dibromo butane : Bromine reacts with the cis isomer to produce $ \left( \pm \right) - 2,3 - $ Dibromo butane, while the trans isomer produces only meso $ - 2,3 - $ Dibromo butane. Hence this is the correct answer.
$ \left( + \right) - 2,3 - $ dibromo butane : The addition of bromine​ to trans but $ - 2 - $ ene does not yield $ \left( + \right) - 2,3 - $ dibromo butane as the product. Hence this is not the correct answer.
$ \left( - \right) - 2,3 - $ dibromo butane : The addition of bromine​ to trans but $ - 2 - $ ene does not yield $ \left( - \right) - 2,3 - $ dibromo butane as the product. Hence this is not the correct answer.
None of the above : Since option A) is the correct answer. This option cannot be considered. Hence this is not the correct answer.
The addition of bromine​ to trans but $ - 2 - $ ene produces meso $ - 2,3 - $ dibromo butane.
Therefore, the correct option is A) meso $ - 2,3 - $ dibromo butane.

Additional Information:
 $ 2 - $ butene is a petrochemical made from catalytic cracking of crude oil or ethylene dimerization. Its basic applications are in the manufacture of gasoline (petrol) and butadiene, while some $ 2 - $ butene is also used to make the solvent butanone by hydration to $ 2 - $ butanol and afterward oxidation.

Note :
Bromine is used in a variety of industries, including agriculture, dyes, insecticides, pharmaceuticals, and chemical intermediates. Few uses are being phased out due to environmental concerns, but new ones are being discovered all the time. Flame retardants can be made from bromine compounds.