Deuterium Compounds

The IR spectra of methyllithium exhibited two C—H bending vibrational modes at 1480 and 1427 cm . Their assignment was again substantiated by significant isotopic shifts to 1100 and 1043 cm in the deuterium compound (Table 1). Only one weak band was observed for ethyllithium in the C—H deformation region at 1450 cm . Moreover, a new sharp peak was detected at 1385 cm and ascribed to the C—H symmetrical bending mode of CH3. Its absence in the IR spectrum of methyllithium is a further indication that free methyl groups exist only in ethyllithium. 

In hydrogen sulfide, phosphine, and the hydrides of their heavier congeners, in which the bonds are nearly normal covalent bonds, the bond angles are observed to be close to 90° (Table 4-1). The values given in the table apply to the deuterium compounds as well as to the protium compounds. 

Simanouti, T. The normal vibrations of polyatomic molecules as calculated by Urcy-Bradley field. II. Vibrations of polythene, ethane, and their deuterium compounds. J. chem. Phys. 17, 734—737 (1949). 

Isotope effects in the range 0-97-T26 have been observed (Table 3) but according to Shiner (1970) an a-deuterium isotope effect close to unity (range 0-97-1-06) indicates a classical SN 2 reaction. The isotope effect is theoretically related to the molecular vibrational frequencies of the initial and transition states for the protium and deuterium compounds. Thus, nucleophilic attack must reduce the change in vibrational frequencies. 

Starting with heavy water as your only source of heavy hydrogen, indicate the steps necessary to prepare each of the following deuterium compounds ... 

Experimentally it has been found that deuterium compounds undergo nitration at the same rate as do the corresponding hydrogen compounds. 

By far the most frequently encountered deuterium compound is D20 or heavy water. This material is generally obtained by enrichment from natural water by electrolysis. 

Bond formation is somewhat weaker with deuterium compounds because the OD distance is somewhat smaller than the OH distance through the lower zero point energy in the first case. 

Denterinm is invariably prepared from heavy water, which itself is mannfactnred by the electrolytic emichment of water, and is available for use as a moderator in nuclear reactors. D2O is useful as a source of deuterium in deuterium-labeled compounds. Deuterium compounds such as heavy water have been extensively studied. In Table 3, a number of physical properties of normal water and heavy water are compared. 

Bartholome and Clusiusi in Eucken s laboratory found the sp. hts. of ordinary and heavy waiter equal, but they are actually quite different, and this may be expected to hold for other hydrogen and deuterium compounds. Ferguson and Cockett found for 99-2 per cent D2O in 20° g.cal. (minimum at41°) ... 

The suggestion which has sometimes been put forward, that the hydrogen atom is not localized but is spread out in the form of a proton cloud, in a similar manner to the single electron in the hydrogen molecule ion, appears most improbable in view of the much greater mass of the proton and the fact that similar bonds occur in deuterium compounds. 

Methyl azide (1) and deuterated methyl azide (CD3N3) were photolysed at 4°K and at 50°K and the products analysed by infrared spectrometry . Methylene imine (3) and the corresponding deuterium compound were observed, presumably formed by a 1,2-hydrogen shift in the nitrene intermediate (2). The vapour phase... 

Deuterium compounds are exactly analogous to those of hydrogen, and arc generally obtained from DgO ... 

Oliphant, Harteck and Rutherford (1934) made the heaviest isotope of hydrogen by bombarding deuterium compounds with deuterons ... 

Leitch, L. C. Synthesis of organic deuterium compounds. XIII. The mechanism of the Nef reaction. Synthesis of ethanal-1-d. Can. J. Chem. 1955, 33, 400-404. 

The resulting spectrum represents a weighted average over the rotational states and a careful analysis of it yields the nuclear quadrupole coupling constant. Molecular beam electric resonance is complementary to pure rotational spectroscopy since transitions between the Stark levels of the rotational states (AJ = 0) are observed (sometimes AJ= 1 transitions are also studied). Specially constructed maser spectrometers55 that can detect transitions of rotationally selected molecules have been used to determine very small coupling constants, such as those for deuterium compounds. Again, molecular beam resonance is currently limited to the study of small molecules. 

The greater availability and cheapness of deuterium compounds, coupled with the large isotope effects, has until recently made this isotope the most widely used in mechanistic studies. However, recent work using nuclear magnetic resonance or mass spectrometry has allowed the determination of heavy atom isotope effects in natural abundance, by... 

Element effects for the hydrogen and deuterium compounds can also be used to distinguish between a concerted E2 mechanism and one with two steps and internal return. Scheme 18.2. Data in Table 18.2 can be used to calculate element effects comparing p-CF3QH4C HClCH2Cl and p-CF3C5H4C HClCH2F where a... 

Note The coupling constant for the deuterium compound is about one order of magnitude smaller than the coupling constant for the H compound. 

Tritium (Table 9.1) occurs in the upper atmosphere and is formed naturally by reaction 9.5, involving neutrons arriving from outer space. Tritium (see Section 2.8) was first obtained synthetically by the bombardment of deuterium compounds such as [ND4]2S04 with fast neutrons, but is now prepared from lithium deuteride, LiF or Mg/Li enriched in 3Li (equation 9.6). 

Preparative methods in which organic molecules are deuterated by means of gaseous deuterium or inorganic deuterium compounds. 

When deuterated compounds were being first prepared, the reduction of aliphatic halogen compounds to the corresponding deuterium compounds was effected mainly by potassium or aluminum amalgam in D20 the preparation of acetic acid from potassium trichloroacetate53 and of methane from bromoform54 may be cited as examples. Later, reduction by zinc in an acid medium was preferred 4d 5 5 for instance, thymine was labelled in the methyl group by reduction of (chloromethyl)uracil with zinc and deuterium chloride 24... 

Although the exchange of the hydroxyl hydrogen in methanol with deuterium in various deuterium compounds such as deuterium oxide and deuterium sulfide has been reported 1-3) and the preparation of methanol-d (CH3OD) by the saponification of esters and decomposition of Grignard reagent with deuterium oxide has been described 4 6), the catalytic exchange of deuterium gas with methanol over Adams platinum catalyst has not been previously studied. 

Large amounts of deuterium compounds are ejqiensive. It is therefore advisable to practice each reaction with light starting material before attempting to use the D compoimds. 

---