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Haloalkanes and Haloarenes

Short Answer Type

141. Haloalkanes are insoluble in water. Give reason.

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Long Answer Type

142. How do the boiling points of R—Cl, R—Br and R—I show variations? Justify your answer.

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Short Answer Type

143. Haloalkanes react with KCN to form alkyl cyanides as main product while AgCN form isocyanides as the chief product. Give reason.

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144.

What are nucleophiles? Give some examples of nucleophiles.

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145.
Write the cause of chemical reactivity of haloalkanes.

In haloalkanes (R—X) the halogen atom (X) is bonded to C atom as —C—X. Now, the halogen atom (X) is more electronegative than carbon. Therefore, the electron cloud of the C—X bond shifts towards X. This causes a polarization of C—X bond. As a result, the C atom acquires a small positive charge (

+) and the halogen atom acquires an equivalent small negative charge (

-). This is represented as

Because of a such rearrangement of the electrons in the C—X bond the haloalkanes (R—X, alkyl halides) are reactive molecules. Consequently, R—
X can be converted into different compounds with different functional groups under proper experimental conditions.

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