Page 208 - Academic Press Encyclopedia of Physical Science and Technology 3rd InOrganic Chemistry

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Main Group Elements 17

double bond (one σ and one π bond). Rather than remain in crustal rocks. Because both these nitrates are highly
double-bond monomers, the heavier elements form cyclic soluble in water, they are not widely distributed and are
oligomers: usually found only as major evaporites in northern Chile
and other extremely arid regions of the globe.
R R
R R In terms of abundance, nitrogen ranks thirty-third
Si
R R
R Si Si R among all elements; but this low ranking belies its impor-
Si Si
R R tance, as evidence by the fact that 5 chemical compounds
R R Si Si containing nitrogen appear among the top 15 chemicals
monomers R Si R
produced in the United States. These five, along with top-
R R
R = same organic group ranked sulfuric acid, are listed in order of rank for the year
1989, below and in Table IV.
If, however, sufficiently bulky R groups are present, their
steric requirements will preclude oligomerization and will
Rank Billions Billions Rank
effectivelyshieldthedoublebond.Someofthestablecom-
by of of by
pounds that have been synthesized include the following: Chemical mass kilograms moles moles
Me
Sulfuric acid, H 2 SO 4 1 39.5 368 5
Ar′ Dinitrogen, N 2 2 24.4 703 2
Ar′ Ar′ Ar′ 5 15.4 865 1
Me Me Ammonia, NH 3
Si Si Ge P Nitric acid, HNO 3 12 7.3 116 11
Ar′ Ar′ Ar′ Ar′′ Urea, (NH 2 ) 2 CO 13 7.0 108 13
t-Bu
Z Ar′′ Ammonium nitrate, NH 4 NO 3 14 6.9 80 17
P P P P Ar′′
Year in and year out sulfuric acid is the top chemical
Z Ar′′ Bu-t t-Bu
produced by weight; but if the rankings were based on
moles, not kilograms, both ammonia and nitrogen would
SiMe 3
be ranked ahead of H 2 SO 4 .
Z C SiMe 3
Atmospheric nitrogen is the ultimate source of all com-
monly used nitrogen compounds. The liquefaction and
SiMe 3
Proof that a double bond is present is best illustrated fractional distillation of air provide the N 2 from which the
by the reactions of a germanium phosphorus compound, important compounds are synthesized. Ammonia is made
an orange crystalline solid. If treated with HCl, HOH, or from N 2 (the Haber process) by reaction with H 2 from
CH 3 OH, the compound undergoes an addition reaction natural gas, nitric acid is made from ammonia in several
similar to alkenes, and its orange color is discharged as it steps, ammonium nitrate is made from the reaction of ni-
forms a saturated colorless product: tric acid with ammonia, urea is made from ammonia and
Ar′ carbon dioxide, and ammonium sulfate is prepared by the
H
HCl Ar′ Ge P reaction of ammonia and sulfuric acid.
Pentane solvent Ar′′
Cl
Ar′ Ar′ A. Hydrides
H
HOH
Ge P Ar′ Ge P
Pentane Ar′′ Ammonia (NH 3 ), hydrazine (N 2 H 4 ), and hydrazoic acid
Ar′ Ar′′ HO
orange Ar′ (HN 3 ) are the most important binary compounds of hydro-
H gen and nitrogen. The first two are bases, but hydrazoic
CH 3 OH Ar′ Ge P
Pentane Ar′′ acid, as its name implies, is weakly acidic.
H 3 CO Ammonia, the most important of the three hydrides of
colorless products nitrogen, is one of the most important of all industrial
chemicals. It is produced by the Haber process, which
brings about the fixation of nitrogen by the direct combi-
VII. NITROGEN
nation of nitrogen and hydrogen under high pressure and
in the presence of a catalyst:
Although the air is ∼75% elemental nitrogen by weight,
◦
nitrogen-containing compounds are not abundant in the Fe,Al 2 O 3 ·K 2 O, 450 C, 250−600 atm
N 2 (g) + 3H 2 (g) −−−−−−−−−−−−−−−−−−→
←−−−−−−−−−−−−−−−−
earth’s crust. Only two minerals, saltpeter (KNO 3 ) and
Chile saltpeter (NaNO 3 ), are found in significant amounts 2NH 3 (g) + 92.2kJ