What are the Optically Active Compounds of C4H9Br?

Learn about the optically active compounds of C₄H₉Br and C₄H₉Br isomers and everything related to the topic.

What are Optically Active Compounds?

The term "optical activity" describes an organic compound's ability to rotate plane-polarized light, which is created when ordinary light is passed through a Nicol prism. These compounds are referred to as optically active compounds and are opposite to nonactive compounds.

A compound can be called optically active if it contains at least one chiral carbon (also termed asymmetric carbon is bonded to four different atoms in a molecule). Even though the compounds include chiral carbons, the presence of any symmetrical element renders the compounds optically inactive. How? Well, the key to the answer is the carbon atom.

The optically active elements and compounds have two non-superimposable mirror-image forms called enantiomers. This happens due to the presence of chiral carbon (as mentioned above) which is attached to different elements. This bonding results in two non-superimposable mirror-image arrangements when exposed to light.

This bonding property enables them to rotate plane-polarized light in opposite directions. This rotation can be either clockwise (dextrorotatory) or counterclockwise (laevo rotatory). On the other hand, optically inactive elements and compounds have equal amounts of both enantiomers and cannot rotate light. In short, chirality in molecules always leads to the rotation of light making them optically active.

Optically Active Compounds of C₄H₉Br

1-bromobutane with the structural formula CH₃(CH₂) ₃Br and chemical formula of C₄H₉Br has a butane molecule (C₄H₉) with one of the hydrogen atoms replaced by a bromine atom (Br). It exists as a clear colorless liquid and is insoluble in water but soluble in organic solvents. Several C₄H₉Br  isomers can exist in different molecular structures but few of them are known to be optically active.

All the possible C₄H₉Br isomers are 1-bromobutane, 2-bromobutane, tert-butyl bromide, and isobutyl bromide. When comparing 1-bromobutane and 2-bromobutane, it can be observed from their molecular structure that 2-bromobutane has two different substituents on both sides while 1-bromobutane has the same substituents attached to the central carbon atom. This arrangement makes 2-bromobutane chiral carbon. So, in other words, isomer 2-bromobutane is optically active and 1-bromobutane isn’t.

Similarly, in between the tert-butyl bromide (2-bromo-2-methylpropane) and isobutyl bromide (2-bromo-2-methylpropane), the latter one is optically active. This is because it contains a a chiral carbon atom whose structure lacks a plane of symmetry giving it a light rotation feature. On the other hand, tert-butyl bromide is rather a special case.

This compound possesses a chiral carbon atom but it has a plane of symmetry in its molecular structure. This happens because of the symmetrical arrangement of three methyl groups around the central carbon atom of this compound. Thus, making it achiral despite having a chiral carbon atom in its center.

Applications of C₄H₉Br as Optically Active Compound:

This compound along with many similar ones is extremely important when studying stereochemistry and synthesis of other chiral compounds including chiral alcohols and chiral amines. These processes directly use C₄H₉Br through substitution or nucleophilic addition reactions.

C₄H₉Br is also commonly used as an electrophile in between the reactions of organolithium or organ magnesium compounds for conducting smooth organometallic reactions. It is also frequently used in educational institutions for the demonstration of chirality, concepts of enantiomers, and stereochemical processes to young chemistry students.

It is not directly used in pharmaceutical companies for drug research but it helps in the synthesis of derivatives or compounds which are very important for R&D purposes in this specific industry. Thanks to its relatively high melting point, it is often used as a solvent in various reactions involving high temperatures and reactants where chirality is needed to be introduced in the final products.

Wrapping Up:

Optical activity is the property of a compound to rotate the plane of polarization of plane-polarized light. Optical activity depends on the chiral center or an asymmetric carbon atom of these compounds. In the four C₄H₉Br isomers, two are optically active due to the presence of chiral carbons. One is not active due to a lack of chiral atoms and the last one has a chiral atom but lacks asymmetry in its molecular structure making it optically inactive. Chiral compounds like this one have a strong impact on industries and the R&D of drugs.