Question

\(\mathrm{CH}_{2} \mathrm{I}_{2}\) is a type of (A) secondary halide (B) vicinal halide (C) geminal halide (D) both (B) and (C)

Short answer

The correct answer is (C) geminal halide, because both iodine atoms in the molecule \(\mathrm{CH}_{2} \mathrm{I}_{2}\) are bonded to the same carbon atom.

Step-by-step solution

Understanding the different types of halides

Before we begin classifying the halide, let's understand the definitions of each type of halide: (A) Secondary halide: A halide in which the carbon atom bonded to the halogen atom is connected to two other carbon atoms. (B) Vicinal halide: A halide in which two halogen atoms are bonded to adjacent carbon atoms. (C) Geminal halide: A halide in which two halogen atoms are bonded to the same carbon atom. (D) Both (B) and (C): This would mean the molecule is both a vicinal and geminal halide.

Analyzing the structure of \(\mathrm{CH}_{2} \mathrm{I}_{2}\)

Now that we know the definitions of the different types of halides, let's analyze the structure of the molecule given, \(\mathrm{CH}_{2} \mathrm{I}_{2}\). In this molecule, there is only one carbon atom bonded to two iodine atoms. There are no other carbon atoms present. So, the structure of this molecule can be represented like this: \(\mathrm{C}( \mathrm{I} )_2 \mathrm{H}_2\)

Classifying the type of halide

Now we can classify the type of halide based on the structure. As there is only one carbon atom present, it is not a secondary halide (option A) since there are no other carbon atoms connected to the carbon bonded to the halogen atoms. Given that there is only one carbon atom in the molecule, there are no adjacent carbon atoms for the halogen atoms to bond to. Therefore, it is not a vicinal halide (option B). However, we can see that both iodine atoms are bonded to the same carbon atom, which matches the definition of a geminal halide (option C). So, \(\mathrm{CH}_{2} \mathrm{I}_{2}\) is a geminal halide. Since it is not a vicinal halide, option (D) (both B and C) is incorrect. Therefore, the correct answer is: (C) geminal halide

Key concepts

Secondary Halide

Secondary halides are a type of organic compound where a single carbon atom, which is bonded to a halogen atom, is also connected to two other carbon atoms. The carbon that holds the halogen is named a secondary carbon. Secondary halides play a significant role in various chemical reactions, particularly in substitution and elimination processes.

When looking at molecular structures of secondary halides, you'll notice the setup of carbon atoms:

• The halogen atom is directly connected to a carbon.
• That carbon is bonded to exactly two other carbons, forming a secondary carbon center.

This bonding aspect is crucial for the categorization of secondary halides, affecting their reactivity and applications in synthetic chemistry. Knowing how to spot these connections can help in predicting how a secondary halide will behave in a reaction.

Vicinal Halide

Vicinal halides are organic compounds featuring halogen atoms attached to adjacent carbon atoms. These are also known as 1,2-dihalides due to the halogens' positions next to each other in the molecular structure.

These structures generally look like this in terms of bonding:

• There are two halogen atoms in the molecule.
• Each halogen atom is bonded to separate, yet neighboring, carbons.

The adjacency of the halogen atoms allows for interesting reactivity. Vicinal halides are notable in synthesis for their role in dehalogenation reactions, often forming alkenes. By understanding the structural makeup of vicinal halides, students can predict the outcome of such transformations.

Vicinal halides are key in organic synthesis, especially when aiming to create double bonds by eliminating halogens.

Geminal Halide

Geminal halides are characterized by having two halogen atoms bonded to the same carbon atom. This unique feature is why they are sometimes referred to as gem dihalides.

The molecular structure of geminal halides includes:

• A single carbon atom bonded to two halogen atoms.
• These halogen atoms are connected to the carbon but not to any other carbons.

In the structure of e.g., dihalomethanes, both halogen atoms are attached to the same central carbon but no neighboring carbon atoms are involved. This arrangement impacts their chemical behavior, often making them less reactive compared to vicinal halides due to the decreased polarity of the molecule.

Geminal halides are common in organic synthesis, particularly in reactions needing the introduction of functionalities or in processes that involve removal of halogen atoms.