Organic Chemistry Essays - Chemistry, Organic Chemistry,

Organic Chemistry Organic compounds are covalently bonded compounds containing carbon, excluding carbonates and oxides. Carbon atoms are unique because of their ability to bond by catenation, which is forming long chains and rings from the covalent binding of an element to itself. Besides bonding with itself, carbon atoms are able to bind to elements with similar electronegativities. Organic compounds consist of carbon and these other elements. Hydrocarbons are the simplest organic compounds, composed of only carbon and hydrogen. Saturated hydrocarbons are hydrocarbons in which each carbon atom in the molecule forms four single covalent bonds with other atoms. Hydrocarbons that contain only single bonds are alkanes. The boiling point for alkanes increases with increasing molecular mass. The carbon-hydrogen bonds of alkanes are nonpolar and the only forces of attraction between nonpolar molecules are weak intermolecular forces. Methane, ethane, propane, and butane are all gases at room temperature. Pentane, octane, and decane are all liquids at room temperature. Heptadecane and eicosane are solids are room temperature. Cycloalkanes are alkanes in which the carbon atoms are arranged in a ring, or cyclic, structure. In fractional distillation, components of a mixture are separated on the basis of boiling point, by condensation of vapor in a fractionating column. The octane rating of a fuel is a measure of its burning efficiency and its antiknock properties. The octane rating scale is based on mixtures of 2,2,4-trimethylpentane, isooctane. Pure 2,2,4-trimethypentane is very resistant to knocking and is assigned an octane number of 100. Pure heptane has an octane number of 0 and burns with a lot of knocking. Increasing the percentage of branched-chain alkanes in gasoline is one way to increase octane rating. Unsaturated hydrocarbons are hydrocarbons in which not all carbon atoms have four single covalent bonds. Alkenes are hydrocarbons that contain double covalent bonds. Alkenes are nonpolar and show trends in properties similar to those of alkanes in boiling points and physical states. -farnesene has 15 carbon atoms and 4 double bonds. It is solid at room temperature and atmospheric pressure. It is found in the natural wax covering of apples. Ethene is the hydrocarbon commercially produced in the greatest quantity in the United States. It is used in the synthesis of many plastics and commercially important alcohols. Ethene is also an important plant hormone. Hydrocarbons with triple covalent bonds are alkynes. This triple bond requires that the simplest alkyne has two carbon atoms. Alkynes, as with other hydrocarbons, exhibit the same trends in boiling points and physical state and are nonpolar. The smallest alkyne, ethyne, is a gas. The combustion of ethyne when it is mixed with pure oxygen produces the intense heat of welding torches. The common name of ethyne is acetylene, and these welding torches are commonly called oxyacetylene torches. Aromatic hydrocarbons are hydrocarbons with six-membered carbon rings and delocalized electrons. Benzene is the primary aromatic hydrocarbon. Benzene rings are chemically very stable, a property that can be explained by the concept of delocalized electrons. Therefore, aromatic hydrocarbons are less reactive than alkenes and alkynes are. Benzene, in the past, was used as a nonpolar solvent because of this stability. However, benzene is both a poison and a carcinogen. It is nonpolar and has limited solubility in water. Another aromatic hydrocarbon, 3,4-benzpyrene, is found in coal tar, tar from cigarette smoke, and soot in heavily polluted urban areas. Shown from studies, this compound is capable of causing cancer. Alcohols are organic compounds that contain one or more hydroxyl groups. The general formula for a class of organic compounds consists of the functional group and the letter R, which stands for the rest of the molecule. The general formula for alcohols is R-OH. Formulas for some alcohols and alkanes are listed below Methanol Butane Ethanol Ethane 1-Propanol Propane Alcohols are sometimes used today as alternative fuels and as octane enhancers in fuel for automobiles. Ethanol is combined with gasoline, for example, in a one-to-nine ratio to produce gasohol. All simple alcohols are poisonous to some extent. When ethanol is consumed, it is broken down by the enzyme alcohol dehydrogenase. Other simple alcohols are attacked by alcohol dehydrogenase more slowly, making these alcohols more toxic then ethanol. For example, methanol, or wood alcohol, is converted to formaldehyde and formic acid, both of which are toxic. Toxic