Question

Consider the following organic compound, \(\stackrel{1}{\mathrm{CH}}_{3}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{CH}_{3}^{7}\) To make it a chiral compound, the attack should be on carbon (a) 1 (b) 4 (c) 3 (d) 6

Short answer

Attack should be on carbon (b) 4.

Step-by-step solution

Identify the Structure

The organic compound given is heptane, which has a structure of: \( \mathrm{CH}_3-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{CH}_2-\mathrm{CH}_3 \). It is a linear alkane with seven carbon atoms and no branches.

Understand Chiral Centers

A carbon atom is chiral if it is bonded to four different groups. In a linear alkane like heptane, each internal carbon is bonded to two hydrogen atoms and two carbon atoms, which are not different groups unless altered.

Determine Site of Alteration

To create a chiral center, we need to replace one of the hydrogen atoms on an internal carbon with a different group (e.g., a halogen, hydroxyl, etc.). The alteration must occur at one of the internal carbon atoms so that four different substituents surround it.

Evaluate Carbon Atoms

Examine the internal carbon atoms for potential conversion to a chiral center: - Carbon 1 and 7 are terminal and attach to three hydrogens and one carbon atom, hence not ideal. - Carbon 2 and 6 already have distinct groups when a new group adds. - Carbon 3 and 5 are symmetrical in a straight chain addition, thus both suitable for different group introduction. - Carbon 4 in the center allows for high versatility in unique group addition given its central position.

Select Optimal Carbon

To make the compound chiral, attack should occur where a new, unique substituent can be added that isn't mirrored along the chain symmetry. Given carbon symmetry in heptane, carbon 4 being in the center is the optimal choice as it ensures unique change with largest differentiation from terminal carbons.

Key concepts

Chiral Centers

Understanding what makes a carbon atom a chiral center is essential for grasping chirality in organic chemistry. A carbon atom becomes a chiral center when it is bonded to four different groups. This arrangement of distinct groups allows for non-superimposable mirror images, known as enantiomers, to arise. These mirror images typically have identical physical properties yet can differ significantly in their chemical behavior, particularly in biological environments. For an alkane like heptane, most carbon atoms are bonded to hydrogens and other carbons symmetrically. To create a chiral center, one of these carbon atoms must be modified by substituting one of its hydrogen atoms with another group, thereby introducing a new element of asymmetry. This is crucial for applications in pharmaceuticals, where chirality can affect how a drug interacts with the body.

Organic Compounds

Organic compounds primarily consist of carbon atoms bonded together with hydrogen, oxygen, nitrogen, or other elements. These compounds form the basis of numerous substances found in living organisms and synthesized products. In organic chemistry, understanding the structure and function of these compounds is fundamental. Carbon's unique ability to form four covalent bonds allows it to act as a versatile backbone for a multitude of organic structures. Organic molecules range from simple hydrocarbons, such as alkanes, to complex macromolecules like proteins and DNA. The versatility and variability of these compounds are central to organic chemistry, encompassing realms from biochemistry to industrial applications.

Alkanes

Alkanes are a fundamental class of organic compounds characterized by carbon and hydrogen atoms only, forming simple structures with single bonds. As saturated hydrocarbons, alkanes follow the general formula of \(C_nH_{2n+2}\). They are known for their chain-like structure, where each carbon atom connects to four atoms—either carbon or hydrogen. The absence of double or triple bonds makes alkanes relatively unreactive compared to other hydrocarbons. The structural simplicity of alkanes also makes them a pivotal starting point for studying more complex molecules and understanding the backbone of various organic reactions. Heptane, for example, is a linear alkane with seven carbon atoms, showcasing the typical properties of this group, including its saturated and non-polar nature.

Carbon Chains

Carbon chains are integral to the structure of organic molecules, serving as the skeleton that holds different functional groups and substituents. These chains can be branched or unbranched (straight), influencing the physical and chemical properties of the molecules they compose. The length and shape of a carbon chain can affect a compound's boiling and melting point, solubility, and reactivity. In linear carbon chains like those found in alkanes, symmetry is common, yet altering this symmetry—such as by creating a chiral center—leads to significant chemical diversity. The ability of carbon to form long and stable chains is a fundamental reason for the diversity and complexity of organic chemistry, providing the structural foundation for countless compounds.