CYCLOHEXANE QUESTION
Neal Howard
>other compounds in an intro organic chem text :) because its bonds (C-C and
>C-H) have little or no dipole moments, and most reactions depend on
>interactions between positive/negative charges or charge asymmetries.
>However, cyclohexanes DO undergo one reaction easily --- they burn!
... and I have a question about the burning of cyclohexane, anybody know
what the comparative octane rating (research number) of cyclohexane is?
I've got a couple of textbooks which list various straight, branched, and
aromatic hydrocarbons' octane numbers (i.e n-heptane = 25
n-hexane = 65
...
...
iso-octane = 100 (reference)
benzene = 106
toluene = 120
racemic xylene = 126)
but there is no mention of cyclohexane. Also is cyclohexane more expensive
than toluene when purchased a couple gallons at a time? Last summer, I found
almost a gallon of benzene in an old machine shop building and used it as
octane booster in my motorcycle and it worked pretty well. I've used small
amounts of toluene (berryman chemtool) but I'm a little leary of dissolving
the neoprene in the fuel lines and carburetor internals with too much
toluene (or xylene). The benzene was almost perfect as an octane booster and
didn't attack neoprene nearly as much as toluene or xylene do. Could
cyclohexane be the miracle spooge I'm looking for or is it too expensive or
does it's fuel performance in a piston engine suck?
Alan S Florjancic
I am pretty sure that it is a bit more expensive than benzene, but don't quote
me on that. The other problem with using it as an octane booster is that it is
a bit on the thick side, as compared to benzene and the like....
Alan Florjancic
The Ohio State University
srg...@grv.grace.cri.nz
ne...@cmptrc.lonestar.org (Neal Howard) writes:
>.... and I have a question about the burning of cyclohexane, anybody know
>what the comparative octane rating (research number) of cyclohexane is?
>I've got a couple of textbooks which list various straight, branched, and
>aromatic hydrocarbons' octane numbers (i.e n-heptane = 25
> n-hexane = 65
> ...
This must be a classic case of "don't always believe what you read".
By definition of both the motor and research octane scales, n-heptane
is always 0 and iso-octane 100. Because 0 to 100 octane ratings are
measured against nC7/iC8 blends, there can be no octane rating for nC7
other than 0. My literature, which correctly gives nC7=0.0 lists
Boiling Actual Blending
Point (C) Research Motor Research Motor
n-hexane 68.7 25 26 19 22
cyclohexane 80.8 83 77 110 97
benzene 80.1 >100 >100 99 91
toluene 110.6 >100 >100 124 112
m-xylene 139.2 >100 >100 145 124
Note that the >100 is correct, because of the definition, octane
numbers above 100 weren't considered octane numbers but "performance
numbers" as either Toluene or alkyl lead compounds had to be
added to the reference fuels to obtain the rating. There are lots of
literature values for individual compounds, but generally blending
values are of most interest, along with boiling point, because
correctly formulated fuels should have octane distributed across their
boiling range 30-220C according to known engine constraints.
Generally, the octane in the front end fraction ( <100C ) is measured
separately to ensure sufficient octane is available there. Both octane
ratings are required to ensure the fuel is suitable for stop/start
driving ( Research ), and sustained high speed driving ( Motor ).
> ...
> iso-octane = 100 (reference)
> benzene = 106
> toluene = 120
> racemic xylene = 126)
> but there is no mention of cyclohexane. Also is cyclohexane more expensive
> than toluene when purchased a couple gallons at a time? Last summer, I found
> almost a gallon of benzene in an old machine shop building and used it as
> octane booster in my motorcycle and it worked pretty well. I've used small
> amounts of toluene (berryman chemtool) but I'm a little leary of dissolving
> the neoprene in the fuel lines and carburetor internals with too much
> toluene (or xylene). The benzene was almost perfect as an octane booster and
> didn't attack neoprene nearly as much as toluene or xylene do. Could
> cyclohexane be the miracle spooge I'm looking for or is it too expensive or
> does it's fuel performance in a piston engine suck?
You can play all sorts of tunes with fuels, but unless you are
modifyiny the engine to use the octane ratings, it's just wasted
effort. Additional octane is usually cheapest when purchased as a
formulated fuel ( gasoline ), as pure chemicals will usually be far
more expensive, but toluene is used because most gasolines have
sufficient front end octane from n-butane (Blending ONs 113) and
i-butane ( blending ONs 122 ) and benzene is comparatively more toxic,
and is now regulated ( 1% in reformulated gasolines ).
Octane above the engine requirement is wasted, and each engine can
have a different octane distribution requirement, but generally
formulated gasolines cover most standard performance engines. The
actual octane of additives is only a small part of the art, how they
synergise with other fuel components ( blending values ) is more
important. Also only factors such as fuel volatility are important as
well. You could find the ethers and alcohols cheap sources of octane
if available. Typical blending M+R/2 octane numbers ( MTBE 110, ETBE
111, TAME 105, EtOH 115, MeOH 119, IPA 108 ).
Bruce Hamilton
srg...@grv.grace.cri.nz
aflo...@magnus.acs.ohio-state.edu (Alan S Florjancic) writes:
>
>I am pretty sure that it is a bit more expensive than benzene, but don't quote
>me on that. The other problem with using it as an octane booster is that it is
>a bit on the thick side, as compared to benzene and the like....
This is not significant, if correct, as the volatility is far more
significant, and their viscosities will be fairly close. Intuitively, I
would have guessed cyclohexane was less viscous - based only on
pouring them from winchesters, certainly the difference would not
affect either carburetted or injected engines.
>Alan Florjancic
>The Ohio State University
Bruce Hamilton
mutt...@gmail.com
Krzysztof Mitko
(in article<e03d6c6f-1447-4cde...@googlegroups.com>):
It’s so-called “Usenet”. Usenet is a network of independent servers,
each of which provides public access to topical groups, such as sci.chem.
Usenet is something fundamentally different than web pages, it predates the
world wide web by a decade. Back in the 1990s there was a company called
Deja, which decided they should provide web-based access to the Usenet and
archived a lot of old messages. Some time after, Deja was bought by Google,
which renamed it to “Google Groups” and added some Google-only forums.
The Usenet, however, is still there: right now I’m using a dedicated usenet
app (not a web browser) to post a message to a server run by a phone company
in Poland. Google will pull this message and put it on their “Google
Groups” page, where you can read it.
--
Chemical engineers do it in packed beds.
IV
news:e03d6c6f-1447-4cde...@googlegroups.com...
> what the comparative octane rating (research number) of cyclohexane is?
https://de.wikipedia.org/wiki/Cyclohexan
"Die Oktanzahl des Cyclohexans ist 77."
https://de.wikipedia.org/wiki/Oktanzahl
the diagram in the picture
You can use e.g. Google Translator.