Which of the following reagents is used to find out carbon-carbon multiple bonds?
A) Grignard reagent
B) Bayer’s reagent
C) Sandmayer’s reagent
D) Gatterman reagent

Hint: Carbon-carbon multiple bonds comes under the group of alkenes and alkynes. There are a lot of methods to detect carbon-carbon multiple bonds in organic compounds. Adding bromine to the compound is an example.

Complete step by step solution:
Let’s explain using each option given above.
A) Grignard reagent is an organo magnesium compound. It has the chemical formula ${\text{R}} - {\text{Mg}} - {\text{X}}$, where \[{\text{R}}\]is any hydrocarbon, \[{\text{Mg}}\]is Magnesium and \[{\text{X}}\]is any halogen. They are used to produce carbon-carbon bonds.

B) Baeyer’s reagent, chemically known as potassium permanganate, is a solution of cold potassium permanganate in alkali. It is of violet color. It is known as a very strong oxidizing agent. Potassium permanganate can be represented chemically as \[{\text{KMn}}{{\text{O}}_4}\]. It has an intense pink or purple color when dissolved in water.
When organic compounds having double or triple bonds react with Baeyer’s reagent, the purple color fades and changes to brown. Aldehydes give a positive result to Baeyer’s test.

C) Aryl halides are produced from aryl diazonium salts in the presence of copper salts as catalysts. This reaction is called the Sandmayer reaction.

D) Gatterman reaction is also known as Gatterman formylation reaction. It is a chemical reaction in which aromatic compounds are formulated by a mixture of \[{\text{HCN}}\]and \[{\text{HCl}}\]in the presence of Lewis acids like \[{\text{AlC}}{{\text{l}}_3}\]. It cannot be used for testing carbon-carbon multiple bonds.

Therefore option B is correct.

Additional information:
Permanganate is also used in fire services. Also used to purify cocaine paste thereby increasing its stability. Also fruit preservation can be done by putting fruits in polyethylene with potassium permanganate.

Note:
Organic material which is oxidisable can be determined using Bayer’s reagent. This value is termed as permanganate value. It has a major role in analytical chemistry. It is used in redox titrations in which it is used as oxidisable titrant.