Ethyl alcohol, commonly known as ethanol, is a clear, colorless liquid with the chemical formula C2H5OH. It is widely used as the active ingredient in alcoholic beverages, a solvent, and an effective antiseptic. The fundamental answer to the question of its bonding is that ethyl alcohol is a covalent compound.
Understanding Chemical Bonds
Chemical compounds are categorized by the type of bond linking their constituent atoms. Ionic bonds form when one atom transfers electrons to another, typically occurring between a metal and a nonmetal. This transfer creates oppositely charged ions held together by strong electrostatic attraction, often resulting in crystalline solids with high melting points.
Covalent bonds form when atoms share electrons, primarily occurring between two nonmetal atoms to form a discrete molecule. Covalent bonds are divided into two types based on the equality of sharing. If electrons are shared almost equally, the bond is nonpolar covalent. If one atom has a stronger pull on the shared electrons, the bond is polar covalent, creating a slight separation of charge, or a dipole.
The Covalent Structure of Ethyl Alcohol
Ethyl alcohol is an organic molecule composed solely of non-metal atoms: Carbon (C), Hydrogen (H), and Oxygen (O). Since there are no metals present in the formula (C2H5OH), the atoms must join together by sharing electrons. This electron sharing confirms that the bonds within the molecule are fundamentally covalent, not ionic.
Within the ethanol molecule, there are distinct types of covalent bonds. The bonds between the two carbon atoms (C-C) and most of the carbon-hydrogen bonds (C-H) are considered nonpolar covalent. The electron sharing in these segments is relatively equal because the electronegativity values of carbon and hydrogen are very similar.
A significant difference arises in the hydroxyl (-OH) functional group attached to one of the carbon atoms. The carbon-oxygen (C-O) and oxygen-hydrogen (O-H) bonds are classified as polar covalent. This polarity results from the oxygen atom’s higher electronegativity, meaning it exerts a greater attractive force on the shared electrons than either the carbon or hydrogen atoms.
Polarity and Unique Properties
The presence of the polar covalent O-H bond gives ethyl alcohol many of its unique characteristics. Oxygen’s strong pull on electrons causes it to develop a partial negative charge, leaving the hydrogen atom with a partial positive charge. This separation of charge across the hydroxyl group creates a permanent molecular dipole, making the overall ethanol molecule polar.
This polarity enables ethanol molecules to engage in strong intermolecular forces, specifically hydrogen bonding. Hydrogen bonding is an attraction that occurs when the partially positive hydrogen atom of one molecule is attracted to the partially negative oxygen atom of a neighboring molecule. This force is responsible for ethanol’s relatively high boiling point compared to nonpolar compounds of similar size.
Versatility as a Solvent
The ability to form these powerful hydrogen bonds is why ethanol is completely miscible with water in all proportions. Water is also a polar molecule that forms hydrogen bonds, and the new hydrogen bonds created between water and ethanol molecules are strong enough to overcome the existing attractions in the pure liquids. The molecule also contains a nonpolar carbon chain, which allows it to dissolve substances that are not water-soluble, making ethanol a versatile solvent for both polar and many nonpolar compounds.