WHICH ONE OF THE FOLLOWING ALKYL HALIDES GIVES THE HIGHEST RATIO OF SUBSTITUTION TO ELIMINATION ON TREATMENT WITH SODUM ETHOXIDE IN ETHANOL
1-BROMOPENTANE
2-BROMOPENTANE
3-BROMOPENTANE
1-BROMO-2-METHYLBUTANE
2-BROMO-2-METHYLBUTANE
Elimination reactions are favored in 3o > 2o > 1o so it seems to me, the way the question is worded, that the answer is the primary halide. Check my thinking.
To determine which alkyl halide gives the highest ratio of substitution to elimination on treatment with sodium ethoxide in ethanol, we need to consider the reactivity of the alkyl halides.
The ratio of substitution to elimination reactions depends on the stability of the carbocation intermediate. If the carbocation is more stable, it is more likely to undergo substitution reactions. On the other hand, if the carbocation is less stable, it is more likely to undergo elimination reactions.
In this case, we can assess the stability of the potential carbocation intermediates by considering the alkyl groups attached to the carbon bearing the positive charge.
Let's examine each alkyl halide:
1-Bromopentane: This alkyl halide has a primary carbocation intermediate. Primary carbocations are the least stable, and thus, this compound is more likely to undergo elimination reactions.
2-Bromopentane: This alkyl halide has a secondary carbocation intermediate. Secondary carbocations are more stable than primary carbocations, and thus, this compound is more likely to undergo substitution reactions.
3-Bromopentane: This alkyl halide has a secondary carbocation intermediate. Similar to 2-bromopentane, it is more likely to undergo substitution reactions.
1-Bromo-2-methylbutane: This alkyl halide has a tertiary carbocation intermediate. Tertiary carbocations are the most stable, and thus, this compound is more likely to undergo substitution reactions.
2-Bromo-2-methylbutane: This alkyl halide also has a tertiary carbocation intermediate. It is also more likely to undergo substitution reactions.
Based on the analysis, both 1-bromo-2-methylbutane and 2-bromo-2-methylbutane have the most stable carbocation intermediates and are, therefore, more likely to undergo substitution reactions. Therefore, the highest ratio of substitution to elimination would be observed with 1-Bromo-2-methylbutane and 2-Bromo-2-methylbutane.