She was a founding member of Pugwash in 1957,
the international organization of scientists who, during
the Cold War, tried to further communication between
scientists on both sides of the Iron Curtain.
Hodgkin was elected a fellow of the Royal Society
in 1947 (in 1956 she received the Royal Medal) and a
foreign member of the Royal Netherlands Academy of
Sciences in 1956 and of the American Academy of
Arts and Sciences (Boston) in 1958. She was the first
woman since Florence Nightingale to become a mem-
ber of the Order of Merit, the most prestigious of
Britain’s royal orders. Between 1977 and 1978 she
was president of the British Association for the
Advancement of Science (awarded the Longstaff
Medal in 1978). In 1982 she received the Lomonosov
Gold Medal because of her respect within the Soviet
scientific community, and in 1987 she received the
Lenin Peace Prize for her commitment to the Soviet
cause and her efforts toward easing tensions between
the East and the West while president of the Pugwash.
She died at her home from a stroke on July 28, 1994,
at age 84.
Hofmann rule “The principal alkene formed in the
decomposition of quaternary ammonium hydroxides
that contain different primary alkyl groups is always
ethylene, if an ethyl group is present.” Originally
given in this limited form by A.W. Hofmann, the rule
has since been extended and modified as follows:
“When two or more alkenes can be produced in a β-
elimination reaction, the alkene having the smallest
number of alkyl groups attached to the double bond
carbon atoms will be the predominant product.” This
orientation described by the Hofmann rule is observed
in elimination reactions of quaternary ammonium
salts and tertiary sulfonium salts, and in certain other
cases.
holoenzyme An ENZYMEcontaining its characteristic
PROSTHETIC GROUP(s) or metal(s).
HOMO (1) An acronym for HIGHEST OCCUPIED
MOLECULAR ORBITAL. (SeeFRONTIER ORBITALs.) (2) A
prefix (consisting of lower case letters, “homo”) used
to indicate a higher homologue of a compound.
homoaromatic Whereas in an AROMATIC molecule
there is continuous overlap of PORBITALs over a cyclic
array of atoms, in a homoaromatic molecule there is a
formal discontinuity in this overlap resulting from the
presence of a single sp^3 hybridized atom at one or sev-
eral positions within the ring; p-orbital overlap appar-
ently bridges these sp^3 centers, and features associated
with aromaticity are manifest in the properties of the
compound. Pronounced homoaromaticity is not nor-
mally associated with neutral molecules, but mainly
with species bearing an electrical charge, e.g., the
homotropylium cation, C 8 H 9 +:In bis, tris, etc. homoaromatic species, two, three,
etc. single sp^3 centers separately interrupt the pi-elec-
tron system.
See alsoHOMOCONJUGATION(2).homoconjugation (1) Association between a base
and its CONJUGATE ACIDthrough a HYDROGEN BOND
(B...HB+ or AH...A–). Homoassociation is a more
appropriate term for this phenomenon.
(2) The orbital overlap of two pi systems separated
by a nonconjugating group, such as CH 2.
See alsoCONJUGATE ACID-BASE PAIR; CONJUGATED
SYSTEM; HOMOAROMATIC.homogeneous catalyst A catalyst existing in the
same phase (solid, liquid, or gas) as the reactants.homogeneous equilibrium Equilibria involving one
species in a single phase, e.g., all gases, all liquids, or
all solids; an equilibrium within a single phase.
See alsoHETEROGENEOUS EQUILIBRIUM.homogeneous mixture Has uniform chemical com-
position, appearance, and properties throughout. Air is
an example.
See alsoHETEROGENEOUS MIXTURE.130 Hofmann rule