Alcohols can be thought of as organic relatives of water: H-O-H water R-O-H alcohol Recall: R stands for a radical, the rest of the molecule. ••

Classification as primary, secondary & tertiary: what kind of carbon is the OH bonded to? CH3CH2CH2CH2OH is a primary (or 1°) alcohol CH3CHCH2CH3 is a secondary (or 2°) alcohol OH

CH3C-OH is a tertiary (or 3°) alcohol CH3

Molecular Geometry & Bonding four e– pairs on O bond angle ~109° e- pairs tetrahedral O R H molecular shape: angular or bent

Nomenclature of Alcohols 1. Find longest carbon chain containing the C-OH. 2. Parent name is alkane + ol = “alkanol” . 3. Number chain so C of C-OH gets lowest possible number.

Example CH3CH2CHCH2CHCH2CHCH3 OH CH2CH3 CH3 5-ethyl-7-methyl-3-octanol

Example 2 CHCH3 CH3 H HO trans-3-isopropylcyclopentanol 2 1 3

The O-H bond of alcohols is polar covalent, just as in water. The permanent dipoles are: O C H d+ d- d+ O-H more polar than O-C other bonds to C

Alcohols form “hydrogen bonds” like water does. A H-bond is an intermolecular attraction between the H of an O-H or N-H bond in one molecule and the unshared electron pairs on :O: or N: in another molecule.

The molecule with the O-H or N-H in the H-bond is the H-bond donor. A molecule that has a N: or :O: particpating in a H-bond is an electron pair donor. It is called a H-bond acceptor.

ROH is both donor & acceptor for H-bonds • H-O = H-bond O-R ROH is both donor & acceptor for H-bonds

H-bonds make a molecule seem heavier -- cause an increase in boiling point compared to other compounds of same molecular weight. CH3CH2-O-CH2CH3 bp 35° C CH3CH2CH2CH2OH bp 118° C