From Wikipedia, the free encyclopedia
Acid anhydrides are chemical compounds that look like, and sometimes are, the product resulting from dehydration of an acid. Most commonly, they form the acid when mixed with water. In organic chemistry, the acids involved are often carboxylic acids; for such cases, please see carboxylic anhydride.
Classically, simple anhydrides arise via the following reaction:
- 2 XOH → X2O + H2O
In principle, such a conversion could describe all known oxides and hydroxides. In practice those of greatest interest have both a stable acid and a stable anhydride.
For a typical mineral acid with formula HxEOy, the fully dehydrated compound has formula EOy-x/2 or E2O2*y-x.
table
| Parent acid |
Intermediate
anhydride
(if any) |
anhydride
|
| perchloric acid, HClO4 |
|
dichlorine heptoxide, Cl2O7 |
| chloric acid, HClO3 |
|
dichlorine pentoxide, Cl2O5 |
| chlorous acid, HClO2 |
|
dichlorine trioxide, Cl2O3 |
| hypochlorous acid, HClO |
|
dichlorine monoxide, Cl2O |
| permanganic acid, HMnO4 |
|
manganese(VII) oxide, Mn2O7 |
| perrhenic acid, HReO4 |
|
rhenium(VII) oxide, Re2O7 |
| pertechnetic acid, HTcO4 |
|
technetium(VII) oxide, Tc2O7 |
| sulfuric acid, H2SO4 |
H2S2O7 |
sulfur trioxide, SO3 |
| sulfurous acid, H2SO3 |
H2S2O5 |
sulfur dioxide, SO2 |
| hyposulfurous acid, H2SO2 |
|
sulfur monoxide, SO |
| selenic acid, H2SeO4 |
|
selenium trioxide, SeO3 |
| selenous acid, H2SeO3 |
|
selenium dioxide, SeO2 |
| orthotelluric acid, Te(OH)6 |
|
tellurium trioxide, TeO3 |
| tellurous acid, H2TeO3 |
|
tellurium dioxide, TeO2 |
| chromic acid, H2CrO4 |
H2Cr2O7 |
chromium trioxide, CrO3 |
| molybdic acid, H2MoO4 |
|
molybdenum(VI) oxide, MoO3 |
| tungstic acid, H2WO4 |
|
tungsten(VI) oxide, WO3 |
| nitric acid, HNO3 |
|
dinitrogen pentoxide, N2O5 |
| nitrous acid, HNO2 |
|
dinitrogen trioxide, N2O3 |
nitrous acid, HNO2
hydrochloric acid, HCl |
|
nitrosyl chloride, NOCl |
nitrous acid, HNO2
Sulfuric acid, H2SO4 |
|
nitrosylsulfuric acid, NOHSO4 |
| phosphoric acid, H3PO4 |
H4P2O7 |
phosphorus pentoxide, "P2O5"
i.e. P4O10 |
| phosphorous acid, H3PO3 |
H4P2O5 |
phosphorus trioxide, "P2O3"
i.e. P4O6 |
| arsenic acid, H3AsO4 |
|
arsenic pentoxide, As2O5 |
| arsenous acid, H3AsO3 |
|
arsenic trioxide, As2O3 |
| carbonic acid, H2CO3 |
|
carbon dioxide, CO2 |
| formic acid, HCOOH |
|
formic anhydride, (HCO)2O |
| stannic acid, H2SnO3 |
|
tin dioxide, SnO2 |
| plumbic acid, H2PbO3 |
|
lead dioxide, PbO2 |
| titanic acid, H2TiO3 |
|
titanium dioxide, TiO2 |
| orthosilicic acid, H4SiO4 |
H2SiO3 |
silicon dioxide, SiO2 |
| orthoboric acid, H3BO3 |
HBO2 |
boron oxide, B2O3 |
| triflic acid, CF3SO2OH |
|
triflic anhydride, (CF3SO2)2O |
