See alsoAMBIDENT; SIGMATROPIC REARRANGEMENT;
TAUTOMERIZATION; VALENCE TAUTOMERIZATION.
tautomerization The ISOMERIZATIONby which tau-
tomers are interconverted. It is a HETEROLYTIC MOLEC-
ULAR REARRANGEMENTand is frequently very rapid.
See alsoTAUTOMERISM.
taxon A grouping of organisms by taxonomic rank,
such as order, family, genus, etc.; also a group of organ-
isms or other taxa sharing a single common ancestor.
tele-substitution A SUBSTITUTION REACTION in
which the ENTERING GROUPtakes up a position more
than one atom away from the atom to which the LEAV-
ING GROUPwas attached.
See alsoCINE-SUBSTITUTION.telomerization The formation of an ADDITION
oligomer, having uniform end groups X′...X′′, by a
CHAIN REACTIONin which a CHAIN TRANSFERlimits the
length of the polymer (“telomer”) produced. An exam-
ple is the polymerization of styrene in bro-
motrichloromethane solution (X′ = CCl 3 , X′′= Br),
where Cl 3 C radicals are formed in the initiation step to
produce Cl 3 C[CH 2 CHPh]nBr, with ngreater than 1 and
often less than 10.temperature A measure of the energy in a substance.
The more heat energy in the substance, the higher is the
temperature. There are a number of temperature scales
that have evolved over time, but three are used presently:
Fahrenheit, Celsius, and Kelvin. The Fahrenheit temper-
ature scale is a scale based on 32 for the freezing point
of water and 212 for the boiling point of water, the
interval between the two being divided into 180 parts.
This scale is named after its inventor, the 18th-century
German physicist DANIEL GABRIEL FAHRENHEIT. The
Celsius or centigrade temperature scale is based on 0
for the freezing point of water and 100 for the boiling
point of water. This scale was invented in 1742 by the
Swedish astronomer ANDERSCELSIUS, and was once
called the centigrade scale because of the 100-degree
interval between the defined points. The Kelvin tem-
perature scale is the base unit of thermodynamic tem-
perature measurement and is defined as 1/273.16 of
the TRIPLE POINT(equilibrium among the solid, liquid,
and gaseous phases) of pure water. The Kelvin is also
the base unit of the Kelvin scale, an absolute-tempera-
ture scale named for the British physicist William
Thomson, Baron Kelvin. Such a scale has as its zero
point absolute zero, the theoretical temperature at
which the molecules of a substance have the lowest
energy.termination The steps in a CHAIN REACTION in
which reactive INTERMEDIATEs are destroyed or ren-
dered inactive, thus ending the chain.ternary acid An acid containing H, O, and another
element, often a nonmetal. Examples are HNO 3264 tautomerization
The formation of an addition oligomer