The organic compounds from a series, known as homologs series in which the successive compounds contain the same functional groups and differ from one another by a –CH2 group. The ―OH group is on the third carbon atom, which is indicated by the name 3-hexanol. Alkyl groups are generally bulkier than hydrogen atoms, however, so the R―O―H bond angle in alcohols is generally larger than the 104.5° H―O―H bond angle in water.

(See chemical bonding for a discussion of hybrid orbitals.) The C–O bond length in ether is almost the same as in alcohols. In the case of alcohols, hydrogen bonds occur between the partially-positive hydrogen atoms and lone pairs on oxygen atoms of other molecules.

10.1 Structure and Classification of Alcohols. The prefix cyclo- is used for alcohols with cyclic alkyl groups. This sigma bond is formed due to the overlap of an sp 3 hybridized orbital of carbon with an sp 3 hybridized orbital of oxygen. In alkanes, the only intermolecular forces are van der Waals dispersion forces. The hydrogen atoms are slightly positive because the bonding electrons are pulled toward the very electronegative oxygen atoms. At four carbon atoms and beyond, the decrease in solubility is noticeable; a two-layered substance may appear in a test tube when the two are mixed.

These attractions become stronger as the molecules lengthen and contain more electrons. Due to the repulsion between the unshared electron pairs of oxygen, the bond angle of C-O-H bonds in alcohols is slightly less than the tetrahedral angle (109°-28′). An ether molecule has a tetrahedral structure. The boiling points of the alcohols increase as the number of carbon atoms increases. At four carbon atoms and beyond, the decrease in solubility is noticeable; a two-layered substance may appear in a test tube when the two are mixed. (See chemical bonding for a discussion of hybrid orbitals.)

For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. Similarly, a tertiary alcohol has the hydroxyl group on a tertiary (3°) carbon atom, which is bonded to three other carbons. Organic chemistry has always been a vast subject of research among science enthusiasts. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. This is the main reason for higher boiling points in alcohols. Number the longest carbon chain starting at the end nearest the ―OH group, and use the appropriate number, if necessary, to indicate the position of the ―OH group. They exhibit a unique set of physical and chemical properties. As with other types of organic compounds, alcohols are named by both formal and common systems. Watch the recordings here on Youtube! This page defines an alcohol, and explains the differences between primary, secondary and tertiary alcohols. Similar to water, an alcohol can be pictured as having an sp3 hybridized tetrahedral oxygen atom with nonbonding pairs of electrons occupying two of the four sp3 hybrid orbitals.