Sutherland died on March 9, 1974, in Miami,
Florida. The Earl Sutherland Prize award is presented
annually by the chancellor of Vanderbilt University to a
Vanderbilt faculty member who has made a nationally
recognized impact in a particular discipline.
Swain-Lupton equation A dual-parameter approach
to the correlation analysis of substituent effects, which
involves a field constant (F) and a resonance constant
(R). The original treatment was modified later. The pro-
cedure has been considerably applied, but also much
criticized.
Swain-Scott equation The LINEAR FREE-ENERGY
RELATIONof the form
lg(k/k 0 ) = snapplied to the variation of REACTIVITYof a given ELEC-
TROPHILIC substrate toward a series of nucleophilic
reagents, where nis characteristic of the reagent (i.e., a
measure of its NUCLEOPHILICITY) and sis characteristic
of the substrate (i.e., a measure of its sensitivity to the
nucleophilicity of the reagent). A scale of nvalues is
based on the rate coefficients kfor the reaction of
methyl bromide with nucleophiles in water at 25°C, s
being defined as 1.00 for these reactions and nbeing
defined as 0.00 for the hydrolysis of methyl bromide.
(Other scales have been devised.)
symbiosis The term was originally applied to
describe the maximum flocking of either hard or soft
LIGANDs in the same complexes. For hydrocarbon
molecules, symbiosis implies that those containing a
maximum number of C–H bonds (e.g., CH 4 ) or C–C
bonds (e.g., Me 4 C) are the most stable.
symproportionation Synonymous with COMPRO-
PORTIONATION.
syn- SeeANTI.
synapse A gap or junction between the ends of two
neurons in a neural pathway where nerve impulses pass
from one to the other. An impulse causes the release of
a neurotransmitter at the synapse that diffuses across
the gap and triggers the next neuron’s electrical
impulse.synaptic terminal(synaptic vesicle) A membrane or
bulb at the end of an axon terminal that stores and
releases neurotransmitters.synartetic acceleration See NEIGHBORING-GROUP
PARTICIPATION.synchronization(principle of nonperfect synchro-
nization) This principle applies to reactions in which
there is a lack of synchronization between bond forma-
tion or bond rupture and other PRIMITIVE CHANGEs
that affect the stability of products and reactants, such
as RESONANCE, SOLVATION, electrostatic, HYDROGEN
BONDING, and POLARIZABILITY effects. The principle
states that a product-stabilizing factor whose develop-
ment lags behind bond changes at the TRANSITION
STATE, or a reactant-stabilizing factor whose loss is
ahead of bond changes at the transition state, increases
the INTRINSIC BARRIERand decreases the “intrinsic rate
constant” of a reaction. For a product-stabilizing factor
whose development is ahead of bond changes, or for
reactant factors whose loss lags behind bond changes,
the opposite relations hold. The reverse effects are
observable for factors that destabilize a reactant or
product.
See alsoIMBALANCE; SYNCHRONOUS.synchronous A CONCERTED PROCESS in which the
PRIMITIVE CHANGEs concerned (generally bond rupture
and bond formation) have progressed to the same
extent as the TRANSITION STATE is said to be syn-
chronous. The term figuratively implies a more-or-less
synchronized progress of the changes. However, the
progress of the bonding change (or other primitive
change) has not been defined quantitatively in terms of
a single parameter applicable to different bonds or dif-
ferent bonding changes. The concept is therefore in
general only qualitatively descriptive and does not
admit an exact definition except in the case of con-synchronous 261