Untitled - Kelly Walsh High School

316 CHEMISTRY FOR THE UTTERLY CONFUSED
The DNA carries the genetic information for the cells. Sections of a DNA molecule
called genes contain the information to make a particular protein. DNA
serves two main functions. Molecules of DNA can produce other DNA molecules
and RNA molecules. RNA molecules are directly responsible for the synthesis
of proteins.
21-8 Utterly Confused About Organic
Reactions problems
Quick Tip
There are far too many organic reactions for us to discuss all of them here. We will
concentrate on a few important types, and give some guidelines on what to look for
in other cases. In most cases, the key to any organic reaction is what functional
group(s) is/are present. Typically, the functional groups will change and nothing else.
A functional group is anything other than a C[C single bond or a C[H bond.
All organic compounds will undergo combustion reactions. That is they will
combine with oxygen gas, O 2, to produce carbon dioxide, CO 2, and water, H 2O.
Nitrogen will yield nitrogen gas, N 2. Most of the halogens will produce the
appropriate hydrogen halide. For example, chlorine, Cl, gives hydrogen chloride,
HCl. The other elements usually give their oxides.
If combustion occurs with a slight deficiency of oxygen then carbon monoxide,
CO, may form instead of carbon dioxide, CO 2. A severe deficiency of oxygen may
result in elemental carbon, C, forming instead of carbon dioxide or carbon
monoxide.
The alkanes are the only organic compounds with no functional group. For this
reason, they do not react readily other than by combustion. However, one of
the few types of reactions in which the alkanes participate are substitution reactions.
As the name implies, something will substitute for something else in the
alkane. Normally the reaction involves an alkane, a halogen (either chlorine or
bromine), and light. Light is necessary to initiate the reaction. In a substitution
reaction of this type, a halogen atom substitutes for a hydrogen reaction. This
process may continue until halogen atoms replace all the hydrogen atoms. To
minimize the opportunity for multiple replacements occurring, an excess of