Deuterated chloroform, also known as chloroform-''d'', is the
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...
with the formula C
2HCl
3 or . Deuterated chloroform is a common
solvent
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
used in
NMR spectroscopy
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic fie ...
. The properties of are virtually identical.
Preparation
Deuterated chloroform is commercially available. It is more easily produced and less expensive than
deuterated dichloromethane
Deuterated dichloromethane (CD2Cl2) is a form (called an isotopologue) of dichloromethane (DCM, CH2Cl2) in which the hydrogen atoms ("H") are replaced with deuterium (heavy hydrogen) isotope ("D"). Deuterated DCM is not a common solvent used in NM ...
.
Deuterochloroform is produced by the reaction of
hexachloroacetone
Hexachloroacetone is an organic compound with the formula (Cl3C)2CO. It is also called hexachloropropanone or perchloroacetone. Numbers indicating the position of the chlorine-atoms are generally omitted as all the possible positions are substitut ...
with deuterium oxide, using
pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a ...
as a catalyst. The large difference in boiling points between the starting material and product facilitate purification by distillation.
:
NMR solvent
In
proton NMR
Proton nuclear magnetic resonance (proton NMR, hydrogen-1 NMR, or 1H NMR) is the application of nuclear magnetic resonance in NMR spectroscopy with respect to hydrogen-1 nuclei within the molecules of a substance, in order to determine the struct ...
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
In nuclear magnetic resonance (NMR) spectroscopy, the chemical shift is the resonant frequency of an atomic nucleus relative to a standard in a magnetic field. Often the position and number of chemical shifts are diagnostic of the structure o ...
of 77.16 ppm with the three peaks being about equal size, resulting from splitting by
spin coupling
In nuclear chemistry and nuclear physics, ''J''-couplings (also called spin-spin coupling or indirect dipole–dipole coupling) are mediated through chemical bonds connecting two spins. It is an indirect interaction between two nuclear spins that ...
to the attached spin-1 deuterium atom (CHCl
3 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 with the 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 them. Chlorine i ...
,
phosgene and
hydrogen chloride
The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride ga ...
. 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
Potassium carbonate is the inorganic compound with the formula K2 CO3. It is a white salt, which is soluble in water. It is deliquescent, often appearing as a damp or wet solid. Potassium carbonate is mainly used in the production of soap and gl ...
may be added. It is less toxic to the liver and kidneys than CHCl
3 due to the presence of a C–D bond which is stronger than a C–H bond. The C–D bond
is stronger than a C–H bond, making it somewhat less prone to form the destructive trichloromethyl radical (•CCl
3).
Regardless, is should be treated as
hepatotoxic
Hepatotoxicity (from ''hepatic toxicity'') implies chemical-driven liver damage. Drug-induced liver injury is a cause of acute and chronic liver disease caused specifically by medications and the most common reason for a drug to be withdrawn fro ...
and is likely to be
carcinogen
A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...
ic.
References
{{DEFAULTSORT:Deuterated Chloroform
Deuterated solvents
Organochlorides
Trichloromethyl compounds
Nuclear magnetic resonance
Deuterated compounds