Deuterated chloroform, also known as chloroform-''d'', is the

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula . Deuterated chloroform is a common

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

used in NMR spectroscopy. The properties of (

chloroform Chloroform, or trichloromethane (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...

) are virtually identical. Deuterochloroform was first made in 1935 during the years of research on

deuterium Deuterium (hydrogen-2, symbol H or D, also known as heavy hydrogen) is one of two stable isotopes of hydrogen; the other is protium, or hydrogen-1, H. The deuterium nucleus (deuteron) contains one proton and one neutron, whereas the far more c ...

Preparation

Deuterated chloroform is commercially available. It is more easily produced and less expensive than deuterated dichloromethane. Deuterochloroform is produced by the reaction of hexachloroacetone with deuterium oxide, using pyridine as a catalyst. The large difference in boiling points between the starting material and product facilitate purification by distillation. : Treating chloral with sodium deuteroxide (NaOD) gives deuterated chloroform.

NMR solvent

In proton NMR spectroscopy, deuterated solvent (enriched to >99% deuterium) is typically used to avoid recording a large interfering signal or signals from the proton(s) (i.e., hydrogen-1) present in the solvent itself. If nondeuterated chloroform (containing a full equivalent of protium) were used as solvent, the solvent signal would almost certainly overwhelm and obscure any nearby analyte signals. In addition, modern instruments usually require the presence of deuterated solvent, as the field frequency is locked using the deuterium signal of the solvent to prevent frequency drift. Commercial chloroform-''d'' does, however, still contain a small amount (0.2% or less) of non-deuterated chloroform; this results in a small singlet at 7.26 ppm, known as the residual solvent peak, which is frequently used as an internal chemical shift reference. In carbon-13 NMR spectroscopy, the sole carbon in deuterated chloroform shows a triplet at a chemical shift of 77.16 ppm with the three peaks being about equal size, resulting from splitting by spin coupling to the attached spin-1 deuterium atom ( has a chemical shift of 77.36 ppm). Deuterated chloroform is a general purpose NMR solvent, as it is not very chemically reactive and unlikely to exchange its deuterium with its solute, and its low boiling point allows for easy sample recovery. It, however, it is incompatible with strongly basic, nucleophilic, or reducing analytes, including many organometallic compounds.

Hazards

Chloroform reacts photochemically with oxygen to form

chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

phosgene Phosgene is an organic chemical compound with the formula . It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. It can be thought of chemically as the double acyl chloride analog of ...

and

hydrogen chloride The Chemical compound, compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hyd ...

. To slow this process and reduce the acidity of the solvent, chloroform-''d'' is stored in brown-tinted bottles, often over copper chips or silver foil as stabilizer. Instead of metals, a small amount of a neutralizing base like potassium carbonate may be added. It is less toxic to the liver and kidneys than due to the stronger bond as compared to the bond, making it somewhat less prone to form the destructive trichloromethyl radical ().

References

{{DEFAULTSORT:Deuterated Chloroform Deuterated solvents Organochlorides Trichloromethyl compounds Nuclear magnetic resonance