Ethanol, or C2H6O, has two different types of bonding between its constituent atoms. The bonds between the hydrogen and carbon atoms are nonpolar covalent bonds. The hydrogen-oxygen and carbon-oxygen bonds are polar covalent bonds. In turn, these polar covalent bonds can lead to hydrogen bonds forming between ethanol molecules and some other molecules.
In a nonpolar covalent bond, the electronegativity values of the two atoms are not significantly different, so they equally share electrons. The electronegativity of hydrogen is 2.20, and the electronegativity of carbon is 2.55. The electronegativity difference of 0.35 between hydrogen and carbon is not strong enough to create a polar covalent bond.
Hydrogen-Oxygen and Carbon-Oxygen Bonds
In a polar covalent bond, the electronegativities of the atoms are sufficiently different enough to bias the shared electrons towards one of the two atoms. The electronegativity of oxygen is 3.44. The difference in electronegativity of the hydrogen-oxygen bond is 1.24. The difference in electronegativity of the carbon-oxygen bond is 0.89. In these bonds, the electrons are more attracted to the oxygen. As a result, this net polar force can lead to hydrogen bonds between two ethanol molecules or with a water molecule.
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