Carbon bonds to many elements other than itself. (a) Name six elements that commonly bond to carbon in organic compounds. (b) Which of these elements are heteroatoms? (c) Which of these elements are more electronegative than carbon? Less electronegative? (d) How does bonding of carbon to heteroatoms increase the number of organic compounds?

In organic chemistry, a heteroatom is any atom that is not carbon or hydrogen. These atoms can significantly influence the structure, reactivity, and properties of organic compounds. Common heteroatoms include oxygen (O), nitrogen (N), sulfur (S), chlorine (Cl), and phosphorus (P).

Heteroatoms contribute to the formation of diverse organic molecules by creating polar bonds, which affect the molecule's solubility, boiling point, and acidity/basicity. Polar bonds are formed due to the difference in electronegativity between carbon and the heteroatom.

For instance:

• Oxygen is highly electronegative and forms polar bonds with carbon, leading to increased solubility in water.
• Nitrogen, while less electronegative than oxygen, can introduce basic sites in the molecule, influencing reactivity.
• Sulfur adds unique reactivity patterns as found in thiols and sulfides.
Heteroatoms also enable the formation of functional groups, which define the chemical behavior of organic compounds. Understanding heteroatoms is essential to predicting the behavior of complex organic molecules.

Electronegativity is the tendency of an atom to attract electrons towards itself in a chemical bond. This property varies across different elements and is crucial in determining the type of bond (polar or non-polar) between atoms.

For example, in a carbon-oxygen bond:

• Oxygen (O) is more electronegative than carbon (C), leading to a polar bond where the electrons are closer to the oxygen atom.
• This polarity can affect the physical properties, such as melting and boiling points, and the reactivity of the molecule.

On the other hand, when carbon forms a bond with an element like hydrogen (H) or nitrogen (N), which are less electronegative, the bond is less polar, affecting the molecule's overall polarity and reactivity.

Elements more electronegative than carbon are oxygen and chlorine, while elements less electronegative include hydrogen, nitrogen, sulfur, and phosphorus.

Knowing the relative electronegativity of the atoms in a molecule helps predict chemical behavior and reactivity, making it a fundamental concept in organic chemistry.

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The presence of different functional groups in organic compounds allows for a vast range of chemical reactivities and properties.

Common functional groups include:

• Hydroxyl group (-OH) found in alcohols.
• Carboxyl group (-COOH) present in carboxylic acids.
• Amino group (-NH2) found in amines and amino acids.
• Sulfhydryl group (-SH) in thiols.
• Phosphate group (-PO4) in phosphates found in DNA and ATP.

The introduction of functional groups by bonding carbon with heteroatoms like oxygen, nitrogen, sulfur, and phosphorus results in compounds with varied chemical properties and biological activities.

For example:

• Alcohols, with their hydroxyl groups, are typically polar and can form hydrogen bonds, influencing their solubility and boiling points.
• Carboxylic acids, containing carboxyl groups, are acidic due to their ability to donate protons (H+).

Functional groups are the cornerstone of organic chemistry, as they determine the structure, reactivity, and interaction of organic molecules in various chemical environments.