Grignard reagent and alcohol reaction give a hydrocarbon as a product which is an alkane compound in most occasions. Alkyl group of Grignard reagents are strong alkalis and nucleophiles. Grignard reagent behaves as a nucleophile and get the hydrogen atom from the alcohol group.
Methyl magnesium bromide reacts with ethanol to give methane. Methyl group in the grignard reagent has a lone pair with a negatice charge. This methyl group attacks the hydrogen atom of -OH group and takes that hydrogen atom towards methyl group. It forms methane.
Ethyl magnesium chloride reacts with propanol to give ethane.
Grignard reagents are strong nucleophiles which can attach positively charged parts. The hydrogen atom in the -OH part of the alcohol is attacked by grignard reagent. Then O-H bond is braked and hydrogen atom connects to the alkyl group of grignard reagent.
Methyl magnesium bromide reacts easily with water to give methane.
Methyl magnesium bromide reacts with CH3Br and gives ethane. But methyl magnesium bromide does not react with CH3CH3.