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Short answer
CDCl3 (deuterated chloroform or chloroform-d) is an isotopically labeled form of chloroform where protium is replaced by deuterium (2H). It is the predominant solvent used in Nuclear Magnetic Resonance (NMR) spectroscopy to dissolve organic compounds without obscuring analyte proton signals, providing spectrometer field locking and standard reference peaks at 7.26 ppm (1H) and 77.16 ppm (13C).
Definition and scope
CDCl3 is the molecular formula for deuterated chloroform, designated by IUPAC as trichloro(deuterio)methane (CAS Registry Number: 865-49-6; PubChem CID: 71583). It is a dense, colorless liquid with a molecular weight of 120.38 g/mol, a boiling point of 60.9 °C to 61.2 °C at 760 mmHg, and a density of 1.500 g/cm³ at 25 °C.
Natural hydrogen contains over 99.98% protium (1H, spin I = 1/2) and roughly 0.015% deuterium (2H or D, spin I = 1). Commercial CDCl3 is synthetically enriched with deuterium to levels between 99.8 atom% D and 99.96 atom% D. This isotopic substitution alters its nuclear magnetic behavior while preserving chloroform’s broad solvent power for small organic molecules.
In chemical research, CDCl3 is the default solvent for reaction monitoring and structure elucidation. Its volatility (boiling point ~61 °C) allows researchers to concentrate solutions on a rotary evaporator and recover purified compounds intact. Handling chlorinated solvents must also follow institutional waste minimization protocols, as outlined in the green chemistry laboratory guide.
How it works or how it is used in practice
In 1H NMR spectroscopy, using standard non-deuterated chloroform (CHCl3) introduces a ~12 M solvent peak that overwhelms detector electronics and obscures analyte multiplets. Deuterating the solvent resolves this via three primary mechanisms:
- Background suppression: Deuterium possesses a distinct gyromagnetic ratio and resonates outside the 1H observation window, reducing background solvent absorption.
- Deuterium field-frequency lock: Modern spectrometers monitor the solvent’s 2H resonance to correct magnetic field drift and temperature variations, maintaining narrow linewidths during acquisition.
- Residual solvent calibration: Commercial CDCl3 contains trace undeuterated CHCl3 (~0.2% in 99.8% D solvent). Per Fulmer et al. (2010) and Gottlieb et al. (1997), this residual protium generates a sharp singlet at 7.26 ppm in 1H NMR. In 13C NMR, coupling between carbon (13C, spin I = 1/2) and deuterium (2H, spin I = 1) splits the carbon resonance into a 1:1:1 triplet centered at 77.16 ppm (coupling constant 1J_CD ≈ 32 Hz).
For absolute zero calibration, manufacturers often supply CDCl3 containing 0.03% to 0.05% v/v tetramethylsilane (TMS), producing singlets defined as exactly 0.00 ppm on both scales.
In routine protocols, 5 to 20 mg of compound is dissolved in 0.5 to 0.7 mL of CDCl3 in a 5 mm glass NMR tube. Organic solutions should be dried over anhydrous agents, such as those covered in the sodium sulfate safety data reference, prior to evaporation. Residual dissolved water (H2O) in CDCl3 appears as a sharp singlet at 1.56 ppm.
Types or related concepts
Laboratories select deuterated solvents based on analyte polarity, isotopic enrichment, and additive formulations. The table below outlines standard CDCl3 grades alongside alternative NMR solvents.
| Solvent Format | Composition & Enrichment | Primary Application | Key Considerations |
|---|---|---|---|
| CDCl3 99.8% D (with TMS) | 99.8 atom% D, 0.03%–0.05% v/v TMS, silver stabilizer | Routine reaction monitoring and standard 1H/13C NMR | Built-in 0.00 ppm reference; silver foil scavenges acidic radicals |
| CDCl3 99.96% D (Ampoules) | 99.96 atom% D, sealed glass ampoules (0.5–1.0 mL) | High-resolution 2D NMR (NOESY, HMBC) and trace analysis | Zero water accumulation; minimal residual 7.26 ppm peak; single-use format |
| CDCl3 99.8% D (TMS-Free) | 99.8 atom% D, no added TMS reference compound | Spectra where analyte peaks overlap with 0.00 ppm | Calibrated against residual CHCl3 (7.26 ppm) and 13C triplet (77.16 ppm) |
| DMSO-d6 | 99.8 atom% D, residual 1H at 2.50 ppm, 13C at 39.52 ppm | Polar compounds, peptides, and salts insoluble in CDCl3 | High boiling point (189 °C); see physical data in the DMSO boiling point guide |
| Methanol-d4 (CD3OD) | 99.8 atom% D, residual 1H at 3.31 and 4.87 ppm; 13C at 49.00 ppm | Polar metabolites, carbohydrates, and coordination complexes | Protic solvent; exchangeable OH and NH protons on analytes exchange with deuterium |
Where it matters for labs, clinics or supply decisions
Procuring and storing CDCl3 requires active quality control because chloroform degrades through photo-oxidation. When exposed to ambient light, oxygen, and trace moisture, CDCl3 undergoes radical decomposition to produce phosgene (COCl2) and deuterium chloride (DCl), alongside trace hydrochloric acid (HCl):
2 CDCl3 + O2 → 2 COCl2 + 2 DCl
While industrial chloroform is stabilized with ethanol or amylene, these organic additives introduce unwanted proton multiplets that ruin NMR spectra. Manufacturers such as Cambridge Isotope Laboratories and Sigma-Aldrich instead use metallic silver foil or wire (approximately 0.5 wt%). The silver scavenges free radicals and precipitates chloride heterogeneously without contaminating the solvent.
Laboratories handling acid-sensitive compounds—such as acetals, ketals, and silyl ethers—must apply specific quality safeguards:
- Acidity testing: Solvent acidity is evaluated by shaking a 1 mL CDCl3 aliquot with neutral water and bromothymol blue indicator. A yellow color indicates significant acid accumulation.
- Bench neutralization: Acidic CDCl3 can be neutralized immediately prior to sample preparation by filtering the solvent through a short pipette plug of basic activated alumina or oven-dried potassium carbonate (K2CO3).
- Continuous-flow workflows: In automated microreactor synthesis (detailed in the microreactor guide), rapid-quench NMR characterization demands verified neutral solvent to avoid post-reaction sample degradation.
Supply managers should choose packaging formats based on laboratory turnover. High-throughput synthesis laboratories benefit from septum-sealed bottles fitted with silver wire. Core facilities and structural biology labs should stock single-use sealed glass ampoules to prevent moisture ingress and phosgene buildup. Because CDCl3 is a volatile, dense halogenated solvent, all sample preparation, transfer, and tube cleaning must occur inside an operational chemical fume hood.
Common misunderstandings
- “CDCl3 produces zero background signals in NMR.” Even 99.8 atom% D solvent contains roughly 0.2% protium, yielding a distinct singlet at 7.26 ppm in 1H NMR and a 1:1:1 triplet at 77.16 ppm in 13C NMR. Dissolved water forms a singlet at 1.56 ppm.
- “Standard laboratory chloroform can substitute for CDCl3 on high-field instruments.” Standard chloroform contains ~12 M proton concentration and organic stabilizers (amylene or ethanol), which overwhelm detector electronics and obscure analyte multiplets.
- “CDCl3 stored at room temperature has an indefinite shelf life.” Air and light accelerate radical degradation into phosgene and DCl. Bottles left unsealed or exposed to daylight turn acidic and destroy acid-labile molecules. CDCl3 should be kept refrigerated at -5 °C to +5 °C in amber glass.
- “Deuterium coupling behaves identically to proton-proton coupling.” Because deuterium has a nuclear spin of I = 1, its coupling to 13C nuclei produces a 2nI + 1 = 3 line pattern (triplet) of equal 1:1:1 intensity, rather than the binomial 1:2:1 triplet resulting from two spin-1/2 protons.
Frequently asked questions
What is CDCl3 used for in chemical research?
CDCl3 is used as a deuterated solvent in Nuclear Magnetic Resonance (NMR) spectroscopy. It dissolves nonpolar to moderately polar organic compounds, suppresses solvent proton signals, and provides a 2H lock signal that stabilizes the spectrometer’s magnetic field during data collection.
Why does CDCl3 appear as a triplet in 13C NMR?
In 13C NMR, the carbon nucleus is directly bonded to one deuterium atom (2H). Because deuterium is a spin I = 1 nucleus, it splits the attached carbon resonance into 2nI + 1 peaks (where n = 1, I = 1), generating a 1:1:1 triplet centered at 77.16 ppm with a coupling constant of approximately 32 Hz.
What is the chemical shift of water in CDCl3?
Residual water (H2O) dissolved in CDCl3 appears as a sharp singlet at 1.56 ppm in 1H NMR spectra. In samples containing acidic impurities or exchangeable hydroxyl protons, this peak can broaden or shift downfield.
Sources
- Cambridge Isotope Laboratories. “Chloroform-d Product Specifications, Storage Guidelines, and Stabilization Technical Bulletin.” https://www.isotope.com/
- Fulmer, Gregory R., Alexander J. M. Miller, Nathaniel H. Sherden, Hugo E. Gottlieb, Abraham Nudelman, Brian M. Stoltz, John E. Bercaw, and Karen I. Goldberg. “NMR Chemical Shifts of Trace Impurities: Common Laboratory Solvents, Organics, and Gases in Deuterated Solvents Relevant to the Organometallic Chemist.” Organometallics 29, no. 9 (2010): 2176–2179. https://doi.org/10.1021/om100106e
- Gottlieb, Hugo E., Vadim Kotlyar, and Abraham Nudelman. “NMR Chemical Shifts of Common Laboratory Solvents as Trace Impurities.” The Journal of Organic Chemistry 62, no. 21 (1997): 7512–7515. https://doi.org/10.1021/jo971176v
- National Center for Biotechnology Information. “PubChem Compound Summary for CID 71583, Chloroform-d.” PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/71583
- Sigma-Aldrich / MilliporeSigma. “Chloroform-d Specification Sheet and MagniSolv NMR Solvents Technical Guide.” https://www.sigmaaldrich.com/
