Imidogen

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Imidogen
Names
IUPAC name
λ1-Azanylidene[1]
Other names
Aminylene

Azanylene
Azanylidene
Imidogen
Nitrene

λ1-azane
hydridonitrogen
Identifiers
3D model (
JSmol
)
ChEBI
ChemSpider
66
  • InChI=1S/HN/h1H checkY
    Key: PDCKRJPYJMCOFO-UHFFFAOYSA-N checkY
  • [NH]
Properties
HN
Molar mass 15.015 g·mol−1
Conjugate acid
Nitrenium ion
Structure
linear
Thermochemistry
21.19 J K−1 mol−1
181.22 kJ K−1 mol−1
Std enthalpy of
formation
fH298)
358.43 kJ mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Imidogen is an

spin multiplicity
.

Production and properties

Imidogen can be generated by

electrical discharge in an atmosphere of ammonia.[3]

Imidogen has a large rotational splitting and a weak spin–spin interaction, therefore it will be less likely to undergo collision-induced

buffer-gas loading from a molecular beam.[3]

The ground state of imidogen is a triplet, with a singlet excited state only slightly higher in energy.[4]

The first excited state (a1Δ) has a long lifetime as its relaxation to ground state (X3Σ) is spin-forbidden.[5] Imidogen undergoes collision-induced intersystem crossing.[4]

Reactivity

Ignoring hydrogen atoms, imidogen is

isoelectronic with carbene (CH2) and oxygen (O) atoms, and it exhibits comparable reactivity.[5] The first excited state can be detected by laser-induced fluorescence (LIF).[5] LIF methods allow for detection of depletion, production, and chemical products of NH. It reacts with nitric oxide
(NO):

NH + NO → N2 + OH
NH + NO → N2O + H

The former reaction is more favorable with a ΔH0 of −408±2 kJ/mol compared to a ΔH0 of −147±2 kJ/mol for the latter reaction.[6]

Nomenclature

The

IUPAC
names, are constructed according to the substitutive and additive nomenclatures, respectively.

In appropriate contexts, imidogen can be viewed as ammonia with two hydrogen atoms removed, and as such, azylidene may be used as a context-specific systematic name, according to substitutive nomenclature. By default, this name pays no regard to the radicality of the imidogen molecule. Although, in even more specific context, it can also name the non-radical state, whereas the diradical state is named azanediyl.

Astrochemistry

Interstellar NH was identified in the diffuse clouds toward

signal-to-noise spectra of the NH A3Π→X3Σ (0,0) absorption band near 3358 Å.[7] A temperature of about 30 K (−243 °C) favored an efficient production of CN from NH within the diffuse cloud.[8][9][7]

Reactions relevant to astrochemistry

Chemical reactions[10][11]
Reaction Rate constant Rate/[H2]2
N + H → NH + e 1×10−9 3.5×10−18
NH2 + O → NH + OH 2.546×10−13 1.4×10−13
NH+
2
+ e → NH + H
3.976×10−7 2.19×10−21
NH+
3
+ e → NH + H + H
8.49×10−7 2.89×10−19
NH + N → N2 + H 4.98×10−11 4.36×10−16
NH + O → OH + N 1.16×10−11 1.54×10−14
NH + C+ → CN+ + H 7.8×10−10 4.9×10−19
NH + H+
3
NH+
2
+ H2
1.3×10−9 3.18×10−19
NH + H+ → NH+ + H 2.1×10−9 4.05×10−20

Within diffuse clouds H + N → NH + e is a major formation mechanism. Near chemical equilibrium important NH formation mechanisms are recombinations of NH+
2
and NH+
3
ions with electrons. Depending on the radiation field in the diffuse cloud, NH2 can also contribute.

NH is destroyed in diffuse clouds by photodissociation and photoionization. In dense clouds NH is destroyed by reactions with atomic oxygen and nitrogen. O+ and N+ form OH and NH in diffuse clouds. NH is involved in creating N2, OH, H, CN+, CH, N, NH+
2
, NH+ for the interstellar medium.

NH has been reported in the diffuse

CH permit studying the carbon, nitrogen and oxygen abundances without resorting to a full spectrum synthesis with a 3D model atmosphere.[15]

See also

References

External links