Question

Draw the structure for 2 -bromo- 2 -chloro- 3 -methylpentane, and indicate any chiral carbons in the molecule.

Short answer

The structure of 2-bromo-2-chloro-3-methylpentane is \( CH_3 - CH^*(CH_3)(Br)(Cl) - CH_2 - CH_2 - CH_3 \), where the chiral carbon (C2) is indicated with an asterisk (*). C2 is chiral because it has four different groups attached: a hydrogen atom, a bromo group, a chloro group, and a carbon chain.

Step-by-step solution

Parent chain identification

To start, identify the longest carbon chain in the molecule. For 2-bromo-2-chloro-3-methylpentane, pentane is the parent chain, which has five carbon atoms. They are numbered from left to right: C1, C2, C3, C4, and C5.

Adding substituents

Add the substituents to the parent chain based on the positions mentioned in the name. - At the 2nd carbon (C2), add a bromo group and a chloro group. - At the 3rd carbon (C3), add a methyl group. The structure after adding the substituents is as follows: \( CH_3 - CH(CH_3)(Br)(Cl) - CH_2 - CH_2 - CH_3 \)

Identifying chiral carbons

Lastly, identify any chiral carbons in the structure. A chiral carbon is one that has four different groups or atoms attached to it. In this case, C2 is the chiral carbon. It has four different groups attached: a hydrogen atom, a bromo group, a chloro group, and a carbon chain. The final structure with the chiral carbon indicated by an asterisk (*): \( CH_3 - CH^*(CH_3)(Br)(Cl) - CH_2 - CH_2 - CH_3 \) In summary, the structure of 2-bromo-2-chloro-3-methylpentane consists of a pentane chain with a bromo and chloro group on C2 and a methyl group on C3. The chiral carbon is C2, which has four different groups attached to it.

Key concepts

Chiral Compounds

Chiral compounds are a fascinating topic in organic chemistry. These are molecules that have a non-superimposable mirror image, much like how your left hand is the mirror image of your right hand and cannot fit perfectly on top of it.
They are very common in nature, including in proteins and other biological molecules. A key feature of chiral compounds is the presence of a chiral center, usually a carbon atom, which is bonded to four different groups. This setup results in two possible configurations (enantiomers) that are mirror images of each other.
In the molecule of 2-bromo-2-chloro-3-methylpentane, carbon 2 ( C_2 ) is the chiral center. It is attached to four different groups: a hydrogen atom, a bromo group, a chloro group, and a carbon chain. This unique arrangement gives rise to chirality in this compound, making it an excellent example when learning about chiral centers and enantiomers.

Chemical Nomenclature

Chemical nomenclature refers to the system of naming chemical compounds in a standardized and universally recognized format. In organic chemistry, the International Union of Pure and Applied Chemistry (IUPAC) has established a set of guidelines for naming compounds.
For our molecule, 2-bromo-2-chloro-3-methylpentane, the name tells you quite a bit about its structure. Here's how it breaks down:

• "Pentane" is the base name, indicating that the parent hydrocarbon chain is five carbon atoms long.
• The numbers (2- and 3-) specify the position of the substituents on the carbon chain, counting from the end closest to the first branch or substituent.
• "Bromo" and "chloro" identify the type of substituents at specific positions ( C_2 ), while "methyl" indicates another substituent on C_3 .

Understanding the IUPAC naming system is crucial because it provides a clear way to deduce the structure of a compound from its name, crucial for communication in science.

Substituents Identification

Substituents are atoms or groups of atoms that replace hydrogen atoms on a parent hydrocarbon chain. Identifying and correctly placing substituents is crucial for the accurate depiction of molecular structures.
In the structural exercise of 2-bromo-2-chloro-3-methylpentane, substituents are added to the pentane backbone.

• A bromo group ( Br ) and a chloro group ( Cl ) are attached to the second carbon ( C_2 ), contributing to the molecule's complexity and chiral nature.
• Additionally, a methyl group ( CH_3 ) is situated on the third carbon ( C_3 ).

Each substituent attachment is specified in the compound's name, emphasizing precision. Practicing identifying and placing substituents aids in mastering structural drawing and understanding molecular behavior, essential skills in organic chemistry.