On Fri, 11 Dec 1998 22:30:26 -0500, John Vallely wrote:
> Hello--
> Any of you folks know what halogenated hydrocarbons are, or what
> products have them?
> --or why I'd want to soak my carburator parts in them?
> Thanks in advance.
> John Vallely
John:
Halogenated hydrocarbons are chemical compounds consisting
of a halogen atom attached to a hydrocarbon. A hydrocarbon is a
relatively simple chemical compound consisting only of carbon and
hydrogen...ethane (C2H6) or propane (C3H8) are examples. The
halogens (I believe "halogens" is greek for "salt formers") are
chemical elements located in group 7 on the periodic table (1 group
to the left of the Noble Elements). They consist of Fluroine,
Chlorine, Bromine, Iodine and Astatine. Now, a halogenated
hydrocarbon is simple a hydrocarbon minus one (or more) of the
hydrogens, which is in turn replaced with a halogen atom. Examples
would be CH3CH2Cl (1-chloroethane), CH3Br (methyl bromide), CHCl3
(chloroform) CH2Cl2 (methylene chloride). There are numerous other
examples, and these types of compounds have many, many applications
in just about all fields.
I'm not sure what automotive products have them...I use numerous
"automotive" solvents but don't remember the contents (except, I
believe the paint removers sold at auto parts stores contain
methylene chloride). So much for being an observant chemist.
Why should you be soaking your carburator parts in these
solvents?? Well, a rule we chemists go by when we think about
solubility of compounds is "like dissolves like." When you consider
what type of solvent to use to dissolve a compound, you consider it's
polarity. If it is polar (meaning, does it have centers of partial
positive or negative charge---hence "poles") you typically choose a
polar solvent...and example is water or ethanol. If it is not polar (meaning
no "poles") you would choose a non-polar solvent....like hexanes, or
petroleum ether.
When you remove automotive parts for cleaning, the "dirt"
that you see is typically grease, excess carbon buildup, fuel
residues or whatever (never contemplated this question). Greases and
fuel residues contain high proportions of non-polar compounds.
Therefore you would choose a non-polar solvent. Halogenated
hydrocarbons can be used, if their chemical makeup imparts non-polar
character to the molecule.
These compounds have their drawbacks...some are
flammable, some have anesthesia qualities, all are toxic. However,
if they are used properly, they are very valuable in the lab, in
industy, medicine, and other applications.
Hope this information (simplistic) helps.
Best Regards,
Matt Milkevitch
'74 BGT
Matthew Milkevitch
Graduate Student, Ph.D. Candidate
Dr. Karen J. Brewer(Chem), Advisor
Dr. Brenda W. Shirley(Biol), Co-Advisor
Va. Tech
Blacksburg, VA 24061
(540) 231-4708
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