http://myweb.yzu.edu.cn/wjhx/ywdw/duwu7.htmSuperacids
A superacid can be defined as an acid that is stronger
than 100 percent sulfuric acid. In fact, chemists have
synthesized superacids that are from 107 to 1019 times
stronger than sulfuric acid. There are four categories
of superacids: Br0nsted, Lewis, conjugate Bronsted-Lewis,
and solid su-peracids. A common Bronsted superacid is
perchioric acid. When per-chloric acid is mixed with
pure sulfuric acid, the sulfuric acid actually acts
like a base:
HClO4(H2SO4)+H2SO4(l) ? H3SO4+(H2SO4)+ClO4－(H2SO4)
Fluorosulfuric acid, HSO3F, is the strongest Bronsted
superacid; it is more than 1000 times more acidic than
sulfuric acid. This superacid, which is an ideal solvent
because it is liquid from – 89℃ to + 164℃, has the
structure shown on the left:
A Bronsted-Lewis superacid is a mixture of a powerful
Lewis acid and a strong Bronsted-Lowry acid. The most
potent combination is a 10 percent solution of antimony
pentafluoride, SbF5, in fluorosulfuric acid. The
addition of antimony pentafluoride increases the acidity
of the fiuo-rosulfuric acid several thousand times.
The reaction between the two acids is very complex,
but the super-hydrogen-ion donor present in the mixture
is the H2SO3F+ ion. This acid mixture will react with
many sub-stances, such as hydrocarbons, that do not
react with normal acids. For example, propene, C3H6,
reacts with this ion to give the propyl cation:
C3H6(HSO3F) + H2SO3F ? C3H7+(HSO3F) + HSO3F(l)
The solution of antimony pentafluoride in fluorosulfuric
acid is commonly called “Magic Acid.” The name
originated in the Case Western Reserve University
laboratory of George Olah, a pioneer in the field of
superacids. A researcher working with Olah put a small
piece of Christmas candle left over from a lab party
into the acid and found that it dissolved rapidiy.
He studied the resulting solution and found that the
long-chain hydrocarbon molecules of the paraffin wax
had added hy-drogen ions, and the resulting cations had
rearranged themselves to form branched-chain molecules.
This unexpected finding suggested the name "Magic Acid,”
and it is now a registered trade name for the com-pound.
This family of superacids is used in the petroleum industry
for the conversion of the less important straight-chain
hydrocarbons to the more valuable branched-chain molecules,
which are needed to produce high-octane gasoline
【 在 lemonstar (super) 的大作中提到: 】
: 【 以下文字转载自 Chemistry 讨论区 】
: 发信人: lemonstar (super), 信区: Chemistry
: 标 题: 请问Superacid指的是什么？
: 发信站: BBS 水木清华站 (Sat Mar 20 20:24:37 2004), 转信
: HCl-HNO3
: SbF5-HSO3Cl
: SbF5-HSO3F
: HClO4-HSO3F
: 以上是哪个？
: 谢谢
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