Halkoarenes & Haloarenes MCQs for NEET — Chemistry Questions with Answers

The NCERT states, 'Grignard reagents are highly reactive and react with any source of proton to give hydrocarbons. Even water, alcohols, amines are sufficiently acidic to convert them to corresponding hydrocarbons.' Anhydrous diethyl ether is the solvent used for its preparation and does not contain active protons to react with the Grignard reagent.

The NCERT text explicitly states, 'In the Grignard reagent, the carbon-magnesium bond is covalent but highly polar, with carbon pulling electrons from electropositive magnesium; the magnesium halogen bond is essentially ionic.'

The NCERT states, 'In the Grignard reagent, the carbon-magnesium bond is covalent but highly polar'. The statement that it is 'primarily ionic' is incorrect; the magnesium-halogen bond is essentially ionic.

Grignard reagents react with any source of proton (or deuteron in this case) to give hydrocarbons. $CH_3MgI$ will abstract a deuteron from $D_2O$ to form $CH_3D$ (deutero-methane), and not methane or iodomethane. The NCERT implies this by stating 'react with any source of proton to give hydrocarbons'.

The NCERT states, 'Alkyl halides react with sodium in dry ether to give hydrocarbons containing double the number of carbon atoms present in the halide. This reaction is known as Wurtz reaction.'

According to the Wurtz reaction, alkyl halides form hydrocarbons with double the number of carbon atoms. If methyl bromide ($CH_3Br$) is used, the product will have $1 imes 2 = 2$ carbon atoms, which corresponds to ethane ($CH_3CH_3$). The NCERT defines the Wurtz reaction as giving 'hydrocarbons containing double the number of carbon atoms present in the halide'.

The NCERT text specifies, 'Alkyl halides react with sodium in dry ether to give hydrocarbons... This reaction is known as Wurtz reaction.'

The NCERT defines Wurtz-Fittig reaction as: 'A mixture of an alkyl halide and aryl halide gives an alkylarene when treated with sodium in dry ether and is called Wurtz-Fittig reaction.'

The NCERT states, 'Aryl halides also give analogous compounds when treated with sodium in dry ether, in which two aryl groups are joined together. It is called Fittig reaction.'

The NCERT highlights this: 'Grignard reagents are highly reactive and react with any source of proton to give hydrocarbons. Even water, alcohols, amines are sufficiently acidic to convert them to corresponding hydrocarbons. It is therefore necessary to avoid even traces of moisture from a Grignard reagent.'