Dictionary of Chemistry [6th Ed.]

phthalic esterAn ester of phthalic
acid. Phthalic esters are made by re-
acting phthalic anhydride with an al-
cohol in the presence of sulphuric
acid. They are high boiling-point liq-
uids used as plasticizers and in the
manufacture of polymers and alkyd
resins. The dimethyl ester is used as
an insect repellent.

phthalocyanineA synthetic com-
pound having molecules with four
isoindole rings linked by –N= bridges.
The structure is similar to that of the
*porphyrins. It can form complexes
with central metal ions. Copper
phthalocyanines are used as dyes.

physical chemistryThe branch of
chemistry concerned with the effect
of chemical structure on physical
properties. It includes chemical ther-
modynamics and electrochemistry.

physisorptionSee adsorption.

phytostigmineSee eserine.

pi-adductAn adduct that is formed

by donation of an electron pair be-

tween a pi orbital and a sigma or pi

orbital.

piano stoolSee sandwich com-

pound.

pi bondSee orbital.

pico-Symbol p. A preÜx used in the

metric system to denote 10–12. For ex-

ample, 10–12farad = 1 picofarad (pF).

picrateA salt or ester of picric acid.

picric acid (2,4,6-trinitrophenol) A

yellow highly explosive nitro com-

pound, C 6 H 2 (NO 2 ) 3 ; r.d. 1.8; m.p.

122 °C.

pi electron An electron in a pi or-

bital. See orbital.

pig iron The impure form of iron

produced by a blast furnace, which is

cast into pigs (blocks) for converting

at a later date into cast iron, steel,

etc. The composition depends on the

ores used, the smelting procedure,

and the use to which the pigs will

later be put.

pinacol rearrangement A reac-

tion in which the diol pinacol, (CH3) 2

COH(CH 3 ) 2 COH, converts to the ke-

tone pinacolone, CH 3 COC(CH 3 ) 3 ,

under acid conditions, with loss of a

molecule of water. A methyl group

moves from one carbon atom to an

adjacent one in order to stabilize

an intermediate carbocation. The

reaction, also called the pinacol-

pinacolone rearrangement, gives its

name to a class of similar rearrange-

ments.

pi orbitalSee orbital.

419 pi orbital

p

N

N N

N

NH N

N NH

Phthalocyanine





























 


Pinacol rearrangement