INTRO - A B C D E F G H I J K L M N O P Q R S T U V-Z - INDEX


E

electrochemical potential:
a measure of the energy change upon transfer of electrons in an oxidation reduction reaction; the measured voltage of an electrochemical cell; the tendency to drive a redox reaction forward. This potential can be measured with a voltmeter and a salt bridge between half cells.

electron spin:
the magnetic field associated with a single electron. Covalent bonds are composed of two electrons each. The pair must be of opposite spin to be allowed in the same molecular orbital. Free radicals have one or more unpaired electrons and are therefore also paramagnetic.

electron transfer:
the movement of electron(s) from one molecule to the other; an oxidation reduction reaction in which the reductant donates electron(s) to the oxidant which accepts them.

electron transport chain:
a series or cascade of electron transfers; a sequential movement of electron(s) from an some primary donor to some final acceptor; a shuttle system for electrons.

electrophile:
a reactive molecule or group which is attracted towards and tends to react with the more electron rich portion of another molecule. Electrophiles can be cations, oxidants, free radicals, or the positive side of a dipole.

emodin:
an anthroquinone found in cascara, senna, and other medicinal herbs. It has antiinfective and possibly antineoplastic effects. The glycoside of emodin is known for its cathartic effects.

endoperoxide:
an organic molecule having two oxygen atoms bound in series as part of a ring structure, the remaining ring members being carbon atoms.

enediol (R-COH=COH-R):
a reactive group composed of two carbon atoms connected by a double bond and having a hydroxyl group bound to each carbon atom. This structure often behaves as a medium strength reductant which can give up one or two hydrogen atoms. Losing two hydrogen atoms produces an alpha-dicarbonyl compound (R-CO-CO-R). This can usually be reduced again and converted back into an enediol.

ene reaction:
the reaction of singlet oxygen with an olefin so as to produce a hydroperoxide.

enol (C=COH-):
a molecular configuration composed of two carbon atoms connected by a double bond with a hydroxyl group at one of the carbon atoms. This structure can tautomerize to become a ketone (CH-C=O).

enzyme:
a naturally occurring catalyst in living things; a protein which catalyses biochemical reactions. Enzymes require substrates which are the reactants upon which they act. Many require cofactors to become active. Many can be modulated by ambient conditions such as pH, redox potential, or the presence of specific inhibitors.

epoxide:
a heterocyclic three element ring consisting of two carbon atoms and one oxygen atom. The sigma bonds of the oxygen atom resemble an ether linkage, except that they are under considerably more angular strain and are less stable. Epoxides can be cleaved by acidic or alkaline solutions and can form various addition products. They can be produced by the addition of one atom of oxygen to an olefin, either from chlorine dioxide or occassionally from ozone. Epoxides are also produced in vivo by action of the cytochrome P450 enzyme complex, which adds one atom of oxygen to the carbon carbon double bond of an aromatic xenobiotic. The resultant epoxide usually rapidly and spontaneously rearranges to form a phenolic compound.

ethylene bridge:
a link between two parts of an organic molecule composed of two carbon atoms bound in between by a double bond.

ethylene diamine tetraacetic acid (EDTA):
a chelating agent possessing two tertiary amino groups and four carboxyl groups. Together these provide six ligands which bind numerous metal cations.

INTRO - A B C D E F G H I J K L M N O P Q R S T U V-Z - INDEX