Encyclopedia of Chemistry

throughout a cyclic array of continuously bonded atoms. It may be viewed as a reaction proceeding through a fully conjugated cyc ...

For systems of more than one chemical component, the concentrations of each are additional variables. A typi- cal two-component ...

Structurally, phospholipids are similar to triglyc- erides except that a phosphate group replaces one of the fatty acids. phosph ...

prises light-harvesting pigments such as CHLOROPHYLL; a primary electron-transfer center, and secondary elec- tron carriers. In ...

in PHOTOPERIODISM and photomorphogenesis. Plant responses regulated by phytochrome include photope- riodic induction of flowerin ...

plasmid An extrachromosomal GENETIC element consisting generally of circular double-stranded DNA, which can replicate independen ...

attached are excluded. Polar effect is then not synony- mous with electronic effect. See also FIELD EFFECT; INDUCTIVE EFFECT; ME ...

light yellow. Some PCBs can exist as a vapor in air. PCBs have no known smell or taste. PCBs have been used as coolants and lubr ...

relates to 0, p= 1, d= 2, and f= 3. The p(principal) orbitals are said to be dumbbell shaped. porins A class of proteins that cr ...

For simple elementary reactions, e.g., A – B + C → A + B – C, the surface can show the potential energy for all values of the A, ...

See alsoKINETIC EQUIVALENCE. pre-exponential factor SeeENERGY OF ACTIVATION; ENTROPY OF ACTIVATION. Prigogine, Ilya(1917–2003) B ...

primitive change One of the conceptually simpler molecular changes into which an ELEMENTARY REAC- TIONcan be notionally dissecte ...

a BRONSTED ACID). The term is preferred to the syn- onym proticor the more ambiguous expression acidic by itself. Also called HB ...

binary compounds. Examples are sodium sulfate (Na 2 SO 4 ), ammonium chloride (NH 4 Cl), and ammo- nium phosphate ((NH 4 ) 3 PO ...

...

QSAR SeeQUANTITATIVE STRUCTURE-ACTIVITY RELA- TIONSHIPS. quantitative analysis The accurate determination of the quantity of a s ...

The differential quantum yield is φ= d[X]/dt n where d[X]/dtis the rate of change of the amount of (substance) concentration of ...

racemic Pertaining to a racemate, an equimolar mix- ture of a pair of ENANTIOMERs. It does not exhibit opti- cal activity. radia ...

(e.g., the benzene radical cation C 6 H 6 +); a negatively charged radical is called a “radical anion” (e.g., the benzene radica ...

ration. Narrow fission tracks from the release of high- energy charged alpha particles burn into the material as a result of the ...