Dinitrogen difluoride is a
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
with the formula . It is a gas at room temperature, and was first identified in 1952 as the
thermal decomposition
Thermal decomposition, or thermolysis, is a chemical decomposition of a substance caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic ...
product of the
fluorine azide (). It has the structure and exists in both
''cis'' and ''trans'' isomers, as typical for
diimides.
Isomers
The ''cis'' isomer has C
2v symmetry and the ''trans'' isomer has C
2h symmetry. These isomers can interconvert, but the process is slow enough at low temperature that the two can separated by low-temperature
fractionation
Fractionation is a separation process in which a certain quantity of a mixture (of gasses, solids, liquids, enzymes, or isotopes, or a suspension) is divided during a phase transition, into a number of smaller quantities (fractions) in which t ...
. The ''trans'' isomer is less
thermodynamically stable but can be stored in glass vessels. The ''cis'' isomer attacks glass over a time scale of about 2 weeks to form
silicon tetrafluoride
Silicon tetrafluoride or tetrafluorosilane is a chemical compound with the formula Si F4. This colorless gas is notable for having a narrow liquid range: its boiling point is only 4 °C above its melting point. It was first prepared in 1771 ...
and
nitrous oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or factitious air, among others, is a chemical compound, an Nitrogen oxide, oxide of nitrogen with the Chemical formula, formula . At room te ...
:
:
Preparation
Most preparations of dinitrogen difluoride give mixtures of the two isomers, but they can be prepared independently.
An aqueous method involves ''N'',''N''-difluoro
urea
Urea, also called carbamide (because it is a diamide of carbonic acid), is an organic compound with chemical formula . This amide has two Amine, amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest am ...
with concentrated
potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash.
Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which utili ...
. This gives a 40% yield with three times more of the trans isomer.
forms a solid unstable compound with
potassium fluoride
Potassium fluoride is the chemical compound with the formula KF. After hydrogen fluoride, KF is the primary source of the fluoride ion for applications in manufacturing and in chemistry. It is an alkali halide salt and occurs naturally as the ...
(or
rubidium fluoride
Rubidium fluoride (RbF) is the fluoride salt of rubidium. It is a cubic crystal with rock-salt structure.
Synthesis
There are several methods for synthesising rubidium fluoride. One involves reacting rubidium hydroxide with hydrofluoric acid: ...
or
caesium fluoride
Caesium fluoride (cesium fluoride in American English) is an inorganic compound with the formula CsF. A hygroscopic white salt, caesium fluoride is used in the synthesis of organic compounds as a source of the fluoride anion. The compound is no ...
) which decomposes to dinitrogen difluoride.
It can also be prepared by
photolysis
Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by absorption of light or photons. It is defined as the interaction of one or more photons wi ...
of
tetrafluorohydrazine
Tetrafluorohydrazine or perfluorohydrazine, , is a colourless, nonflammable, reactive inorganic gas. It is a fluorinated analog of hydrazine.
Synthesis
Tetrafluorohydrazine was originally prepared from nitrogen trifluoride using a copper as a f ...
and
bromine
Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...
:
:
Reactions
The ''cis'' form of difluorodiazene will react with strong fluoride ion acceptors such as
antimony pentafluoride
Antimony pentafluoride is the inorganic compound with the formula Sb F5. This colorless, viscous liquid is a strong Lewis acid and a component of the superacid fluoroantimonic acid, formed upon mixing liquid HF with liquid SbF5 in 1:1 ratio. It ...
to form the
linear
In mathematics, the term ''linear'' is used in two distinct senses for two different properties:
* linearity of a '' function'' (or '' mapping'');
* linearity of a '' polynomial''.
An example of a linear function is the function defined by f(x) ...
cation (fluorodiazonium cation
) which forms a
salt
In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
with the formula (fluorodiazonium hexafluoroantimonate(V)).
:
Analogous reaction of ''cis''-difluorodiazene with
arsenic pentafluoride
Arsenic pentafluoride is a chemical compound of arsenic and fluorine. It is a toxic, colorless gas. The oxidation state of arsenic is +5.
Synthesis
Arsenic pentafluoride can be prepared by direct combination of arsenic and fluorine
Fluorine is ...
gives white solid salt with the formula
(fluorodiazonium hexafluoroarsenate(V)).
:
In the solid phase, the observed and bond distances in the cation are 1.089(9) and 1.257(8) Å respectively, among the shortest experimentally observed N-N and N-F bonds.
References
{{Nitrogen compounds
Inorganic nitrogen compounds
Nitrogen fluorides
Nonmetal halides