Distinguish between the following pair: (i) Bromo benzene & benzyl bromide (ii) nPropyl alcohol & iso-propyl alcohol

Let's break down the differences between the pairs you've mentioned: bromo benzene and benzyl bromide, as well as n-propyl alcohol and iso-propyl alcohol. Each pair consists of compounds that may seem similar at first glance but have distinct structural and chemical properties.

Bromo Benzene vs. Benzyl Bromide

Bromo benzene and benzyl bromide are both aromatic compounds that contain bromine, but they differ significantly in their structures and reactivity.

Structure

• Bromo Benzene: This compound has a bromine atom directly attached to a benzene ring. Its structure can be represented as C6H5Br, where the bromine replaces one hydrogen atom on the benzene.
• Benzyl Bromide: In contrast, benzyl bromide has a bromine atom attached to a benzyl group, which consists of a benzene ring connected to a CH2 group. Its formula is C6H5CH2Br.

Reactivity

The positioning of the bromine atom affects how these compounds react. Bromo benzene is less reactive in nucleophilic substitution reactions because the aromatic ring stabilizes the structure, making it less likely to undergo such reactions. On the other hand, benzyl bromide is more reactive due to the presence of the CH2 group, which allows for easier displacement of the bromine atom in nucleophilic reactions.

n-Propyl Alcohol vs. Iso-Propyl Alcohol

Now, let's look at the second pair: n-propyl alcohol and iso-propyl alcohol, which are both alcohols but differ in their molecular structures.

Structural Differences

• n-Propyl Alcohol: Also known as 1-propanol, this compound has the hydroxyl (-OH) group attached to the first carbon of a straight-chain propyl group. Its structure can be represented as CH3-CH2-CH2OH.
• Iso-Propyl Alcohol: Commonly referred to as 2-propanol or isopropanol, this alcohol has the hydroxyl group attached to the second carbon of the propyl chain, resulting in a branched structure: CH3-CHOH-CH3.

Physical and Chemical Properties

The structural differences lead to variations in their physical properties. For instance, iso-propyl alcohol has a lower boiling point compared to n-propyl alcohol due to its branched structure, which affects how the molecules pack together. In terms of reactivity, both alcohols can undergo similar reactions, but iso-propyl alcohol is often more commonly used as a solvent and disinfectant due to its effectiveness and lower toxicity.

In summary, while bromo benzene and benzyl bromide differ in their bromine attachment and reactivity, n-propyl alcohol and iso-propyl alcohol vary in their structure and some physical properties. Understanding these distinctions is crucial for applications in organic chemistry and industrial processes.