Dictionary of Chemistry [6th Ed.]

Autocatalysis occurs as in the

*Lotka–Volterra mechanism and the

*oregonator. If the concentrations of

A and B are maintained constant, the

concentrations of X and Y oscillate

with time. A graph of the concentra-

tion of X against that of Y is a closed

loop (the limit cycle of the reaction).

The reaction settles down to this

limit cycle whatever the initial con-

centrations of X and Y, i.e. the limit

cycle is an *attractor for the system.

The reaction mechanism is named

after the city of Brussels, where the

research group that discovered it is

based.

Buchner funnelA type of funnel

with an internal perforated tray on

which aÛat circularÜlter paper can

be placed, used forÜltering by suc-

tion. It is named after the German

chemist Eduard Buchner (1860–

1917).

buckminsterfullerene A form of

carbon composed of clusters of 60

carbon atoms bonded together in a

polyhedral structure composed of

pentagons and hexagons (see illustra-

tion). Originally it was identiÜed in

1985 in products obtained byÜring a

high-power laser at a graphite target.

It can be made by an electric arc

struck between graphite electrodes

in an inert atmosphere. The mol-

ecule, C 60 , was named after the US

architect Richard Buckminster Fuller

(1895–1983) because of the resem-

blance of the structure to the geo-

desic dome, which Fuller invented.

The molecules are informally called

buckyballs; more formally, the sub-

stance itself is also called fullerene.

The substance is a yellow crystalline

solid (fullerite), soluble in benzene.

Various fullerene derivatives are

known in which organic groups are

attached to carbon atoms on the

sphere. In addition, it is possible to

produce novel enclosure compounds

by trapping metal ions within the C 60

cage. Some of these have semicon-

ducting properties. The electric-arc

method of producing C 60 also leads

to a smaller number of fullerenes

such as C 70 , which have less symmet-

rical molecular structures. It is also

possible to produce forms of carbon

in which the atoms are linked in a

cylindrical, rather than spherical,

framework with a diameter of a few

nanometres. They are known as

buckytubes(or nanotubes).

A

• Information about IUPAC nomenclature
  and representation of fullerenes and
  related compounds

Buchner funnel 86

b

Buckminsterfullerene

buckyballSee buckminster-

fullerene.

buckytubeSee buckminster-

fullerene.

buffer A solution that resists

change in pH when small amounts of

an acid or alkali are added over a cer-

tain range or when the solution is di-

luted. Acidic buffers consist of a

weak acid with a salt of the acid. The

salt provides the negative ion A–,

which is the conjugate base of the

acid HA. An example is carbonic acid