Hydrogen deuteride

Hydrogen deuteride is an isotopologue of dihydrogen composed of two isotopes of hydrogen: the majority isotope ¹H (protium) and ²H (deuterium). Its proper molecular formula is ¹H²H, but for simplification, it is usually written as HD.

Hydrogen deuteride

Skeletal formula of hydrogen deuteride
Names
IUPAC name Hydrogen deuteride
Systematic IUPAC name (2H)Dihydrogen[citation needed]
Identifiers
CAS Number	13983-20-5 Y
3D model (JSmol)	Interactive image
ChemSpider	146609 Y
ECHA InfoCard	100.034.325
EC Number	237-773-0
PubChem CID	167583
UN number	1049
CompTox Dashboard (EPA)	DTXSID001027186
InChI InChI=1S/H2/h1H/i1+1 Y Key: UFHFLCQGNIYNRP-OUBTZVSYSA-N Y InChI=1/H2/h1H/i1+1 Key: UFHFLCQGNIYNRP-OUBTZVSYED
SMILES [2H][H]
Properties
Chemical formula	HD
Molar mass	3.02204 g mol−1
Melting point	−259 °C (−434.2 °F; 14.1 K)
Boiling point	−253 °C (−423.4 °F; 20.1 K)
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H220, H280
Precautionary statements	P210, P377, P381, P403, P410+P403
NFPA 704 (fire diamond)	0 4 0
Autoignition temperature	571 °C (1,060 °F; 844 K)
Related compounds
Related hydrogens	Deuterium Hydrogen Tritium
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Preparation and occurrence

In the laboratory it is produced by treating sodium hydride with deuterated water:^[1]

NaH + D₂O → HD + NaOD

Hydrogen deuteride is a minor component of naturally occurring molecular hydrogen. It is one of the minor but noticeable components of the atmospheres of all the giant planets, with abundances from about 30 ppm to about 200 ppm. HD has also been found in supernova remnants,^[2] dense interstellar clouds,^[3] and protoplanetary disks.^[4][5]

Occurrence of HD vs. H₂ in giant planets' atmospheres

Planet	HD	H2
Jupiter	~0.003%	89.8% ±2.0%[6]
Uranus	~0.015%	82.5% ±3.3%[7]
Neptune	~0.019%	80.0% ±3.2%[8]

H NMR spectrum of a solution of HD (labeled with red bars) and H₂ (blue bar). The 1:1:1 triplet arises from the coupling of the ¹H nucleus (I = 1/2) to the ²H nucleus ( I = 1).

Radio emission spectra

HD and H₂ have very similar emission spectra, but the emission frequencies differ.^[9]

The frequency of the astronomically important J = 1-0 rotational transition of HD at 2.7 THz has been measured with tunable FIR radiation with an accuracy of 150 kHz.^[10] In astronomy, this J = 1-0 line has been used to determine the masses of protoplanetary disks surrounding T Tauri stars^[4] and Herbig Ae/Be stars.^[5]

See also: rotational spectroscopy