formaldehyde - Sciencemadness Dot Org

Chapter 15
Reactions of Formaldehyde with Hydrocarbons
and Hydrocarbon Derivatives
Under appropriate conditions of catalysis, temperature, etc., formaldehyde
reacts with a -wide variety of unsaturated aliphatic and aromatic
hydrocarbons. These reactions, together with those encountered with
hydrocarbon derivatives such as halogenated hydrocarbons, nitrohydrocarbons,
and organometallic compounds, will be reviewed in the following
pages. To date, we know of no clear-cut instances in which, paraffins have
been successfully reacted with formaldehyde.
Although nitroparaffins and organometallic compounds react readily
with formaldehyde, unsubstituted olefins, aromaties and nitro-aromatics
as well as their halogen derivatives react only in the presence of strong acids.
The simplicity of the formaldehyde molecule gives it a good degree of
chemical stability to acids. This property is not generally shared by the
more complicated aldehydes and carbonyl compounds, which tend to decompose
or undergo auto-condensation reactions when treated with acidic
compounds. As a result of its stability, formaldehyde can be successfully
employed for many organic syntheses in cases where extremely stringent
conditions are required to initiate reactions. In some cases acids apparently
unite with formaldehyde to give simple addition products which
function as reaction intermediates without destroying the integrity of the
formaldehyde molecule. This is similar to the manner in which methylene
glycol acts as an intermediate in all reactions involving aqueous formaldehyde,
Reactions with Olefins and Cyclo-olefins
Reactions of formaldehyde with hydrocarbons containing the ethylenic
linkage usually result in the formation of 1,3-gIycoIs, unsaturated alcohols,
aad functional derivatives of these compounds. Ethylene itself apparently
does not react readily, and satisfactory methods for conducting ethyleneformaldehyde
reactions have not been found to date in the chemical literature.
Fundamentally, reactions may be envisaged as involving the addition
of methylene glycol to the carbon-carbon double bond as shown below:
\ / X /
C=c + HO—CHaOH > O-C—
/ \ /I I
OH CH,OH
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