Grignard's reagents give alkanes by reaction with alcohols.

Answer

To understand how Grignard reagents react with alcohols to produce alkanes, let's break down the process step by step.

### Step 1: Identify the Reactants
We start with two reactants:
- An alcohol, represented as \( ROH \) (where \( R \) is an alkyl group and \( OH \) is the hydroxyl group).
- A Grignard reagent, represented as \( R'MgX \) (where \( R' \) is another alkyl group and \( X \) is a halogen).

### Step 2: Write the Reaction Equation
The general reaction can be written as:
\[ ROH + R'MgX \rightarrow R'H + R'OMgX \]
Here, \( R'H \) is the alkane produced, and \( R'OMgX \) is the byproduct.

### Step 3: Understand the Mechanism
1. The Grignard reagent \( R'MgX \) acts as a strong nucleophile. It will attack the hydrogen atom of the hydroxyl group in the alcohol.
2. This results in the formation of an alkane \( R'H \) and a magnesium alkoxide \( R'OMgX \).

### Step 4: Example
Let’s take methanol (\( CH_3OH \)) as an example of an alcohol and ethyl magnesium bromide (\( C_2H_5MgBr \)) as a Grignard reagent:
\[ CH_3OH + C_2H_5MgBr \rightarrow C_2H_6 + C_2H_5OMgBr \]
In this reaction:
- The product \( C_2H_6 \) is ethane, which is the alkane formed.
- The byproduct \( C_2H_5OMgBr \) is the magnesium alkoxide.

### Step 5: Conclusion
Thus, the statement that Grignard reagents give alkanes by reaction with alcohols is true. The reaction results in the formation of an alkane and a magnesium alkoxide.

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