deuterium
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| General | ||||||||||||||||
| Surname | deuterium | |||||||||||||||
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| Molecular formula | D 2 (molecular form) | |||||||||||||||
| Brief description |
colorless and odorless gas |
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| Physical state |
gaseous |
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| density |
0.17 kg m −3 |
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| Melting point |
−254.43 ° C |
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| boiling point |
−249.58 ° C |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||||||||
Deuterium (from ancient Greek δεύτερος deúteros , "the second") is a natural isotope of hydrogen . Its atomic nucleus is also called a deuteron and consists of a proton and a neutron . Deuterium ( 2 H) is also known as "heavy hydrogen" because of its mass. It was discovered in 1931 by the American chemists Harold C. Urey and Ferdinand Brickwedde and George Murphy. Urey received the Nobel Prize in Chemistry for this in 1934 .
The other two natural isotopes of hydrogen are protium ( 1 H) and tritium ( 3 H). Due to the great importance of the isotopes and because the masses differ greatly, separate symbols are also used for the isotopes deuterium and tritium: D and T.
The name deuterium comes from Gilbert Newton Lewis (Urey's teacher), who was also the first to produce heavy hydrogen. Evidence of the isotope already existed with the development of mass spectrometry in the 1920s.
description
The chemical symbol is 2 H; for the sake of simplicity in the formula notation, D is also often used.
In contrast to 1 H hydrogen, whose atomic nucleus consists of only one proton , the deuterium nucleus contains a neutron in addition to this proton . The proportion of deuterium in naturally occurring hydrogen is 0.015 percent.
It is assumed that deuterium was created in primordial nucleosynthesis immediately after the Big Bang , because the deuterium formed in stellar nucleosynthesis fuses to helium after a short time . That is why the frequency of deuterium in the cosmos is an important parameter for cosmological models.
In the simplest case, two deuterium atoms combine chemically to form a deuterium molecule. There are two variants, depending on the total spin I G of the molecule, the orthodeuterium (oD 2 ) if the nuclear spin isomer has total spin 0 or 2, and the paradeuterium (pD 2 ) in the case of I G = 1.
Due to its low frequency, it occurs in nature almost exclusively in the form of the HD molecule.
Occurrence
The natural abundance of the isotope deuterium is 0.015 percent. The water occurring on earth (1.4 billion cubic kilometers or 1.4 · 10 18 tons) consists of around one ninth (2 u of 18 u) or 11.19 percent of its mass from hydrogen (including deuterium), therefore it contains 0.0035 percent or 5 · 10 13 tons of deuterium. This is mainly bound as DHO and very rarely as D 2 O.
Furthermore, there are almost 10 tons of tritium in the world's oceans.
Extraction
Due to the large relative mass difference, deuterium can be enriched more easily than the isotopes of other elements such as B. uranium . The Girdler sulfide process is usually used in the first enrichment stages . This exploits the fact that in an aqueous hydrogen sulfide solution the hydrogen atoms and the deuterium atoms swap their places between the two types of molecule: At low temperatures, the deuterium migrates preferentially into the water molecule, at high temperatures into the hydrogen sulfide molecule. In the last enrichment stage, the mixture of H 2 O, HDO and D 2 O is separated by distillation .
In addition to the Girdler sulfide process, deuterium can also be enriched through distillation and electrolysis.
Applications
Deuterium is used as a moderator in nuclear reactors (here in the form of heavy water), as fuel in hydrogen bombs and in future in nuclear fusion reactors , as a replacement for protium (ordinary hydrogen) in solvents for 1 H NMR spectroscopy and as a tracer in chemistry and Biology. There it is also an important isotope label in NMR spectroscopy (especially solid-state NMR ) in order to detect the dynamics in organic substances and to clarify structures. Gaseous deuterium is also used in special lamps in photometers, e.g. B. in atomic spectroscopy as a source of UV light.
Heavy water
If the hydrogen in water (H 2 O) is replaced by deuterium , heavy water (D 2 O) is obtained. In mixtures, semi-heavy water (HDO) is statistically also present due to the rapid exchange of protons and deuterons.
The density of D 2 O is 1.1047 g · cm −3 at 25 ° C, the melting point is 3.8 ° C and the boiling point is 101.4 ° C. The density maximum is 11.2 ° C (water: 3.98 ° C). These differences in physical properties compared to water are known as the isotope effect . It is most pronounced among all nuclides between 1 H and 2 H.
Heavy water slows down or prevents many metabolic processes, which is why most living things are only partially viable with a very high deuterium content.
- Heavy water has a reduced dissolving power compared to normal water.
- Deuterons have a lower tunneling capacity than protons and therefore make it difficult to maintain the electrochemical gradients on mitochondrial membranes in biological systems . However, these are crucial for the synthesis of ATP .
- The functionality of most proteins depends on the mobility of the surrounding water molecules. Since deuterons are more sluggish because of their greater mass, the proteins can only perform their tasks less or not at all.
safety instructions
Deuterium is not listed in Annex VI of Regulation (EC) No. 1272/2008 (CLP) , but in this respect it is to be regarded as hydrogen, since all isotopes of an element are very similar in terms of their chemical behavior and danger.
Individual evidence
- ↑ a b Air Liquide: Deuterium .
- ↑ a b Entry on Deuterium. In: Römpp Online . Georg Thieme Verlag, accessed on May 27, 2013.
- ↑ a b Entry on Deuterium in the GESTIS substance database of the IFA , accessed on July 23, 2016(JavaScript required) .
- ↑ Derek Lowe, Das Chemiebuch, Librero 2017, p. 286
- ↑ goehler-hplc.de: UV photometer lamps (deuterium lamps ) , accessed on May 27, 2013.
