http://www.ck12.org Chapter 25. Organic Chemistry
TABLE25.2:Alkanes
Compound Formula Molar Mass (g/mol) Boiling Point (°C)
ethane CH 3 CH 3 30 − 88
methanol CH 3 OH 32 64.7
propane CH 3 CH 2 CH 3 44 −42.1
ethanol CH 3 CH 2 OH 46 78.3Only weak London dispersion forces hold molecules of nonpolar alkanes together in the liquid phase. Consequently,
less energy is required to break these molecules away from the surface of the liquid and turn them into a vapor.
The boiling points of small alkanes are low. The stronger hydrogen bonding between alcohol molecules means that
more energy is required to convert the liquid to vapor, resulting in significantly higher boiling points. Because all
molecules display London dispersion forces, the total strength of the intermolecular forces and, therefore, the boiling
point, increases along with molar mass for groups of similar compounds.
Alcohols are commonly found in many everyday materials (Figure25.18). Hand sanitizers typically contain
ethanol or isopropanol (2-propanol). Isopropanol (rubbing alcohol) is also used as a common antiseptic. Ethylene
glycol (1,2-ethanediol) is the active ingredient in most commercial antifreezes. A 50% by volume solution of
ethylene glycol freezes at−36°C. Glycerol (1,2,3-propanetriol) is a very viscous alcohol that is frequently used
as a moistening agent in cosmetics.
FIGURE 25.18
Some of the many household products
that contain one or more alcohols include
hand sanitizer and cosmetics such as lip-
stick.Fermentation is a process in which sugars, such as glucose or fructose, are converted into ethanol and carbon dioxide.
Fermentation is used in the production of wine, beer, and other spirits. The ethanol in these beverages, like all simple
alcohols, is toxic to some extent. Ethanol is metabolized to acetaldehyde within the body. These compounds are
fatal in large enough doses. Methanol is lethal in even smaller doses than ethanol because the body converts it into
formaldehyde and formic acid, which are extremely toxic. Ethylene glycol is also quite toxic. Its sweet smell and
taste makes it very dangerous to dogs and other animals that may drink spilled antifreeze. Many antifreezes now use
the much safer propylene glycol (1,2-propanediol) instead of ethylene glycol.
Ethers
Anetheris an organic compound in which two hydrocarbon groups are bonded to the same oxygen atom. An ether
is represented by the general formula R−O−R’. The R’ in the formula means that the second hydrocarbon group
(R’) may be different from the first one (R). The steps for naming ethers are listed below.
- The wordetherappears at the end of the name.