# The carbon-13 NMR for 1,1,1-trichloroethane

I was working the following spectroscopy problem from Clayden 2e that asks us to identify the structure of a compound from information about its carbon-13 NMR peaks.

Problem 3.5: The solvent formerly used in some correcting fluids is a single compound $$\ce{C2H3Cl3}$$, having 13C NMR peaks at 45.1 and 95.0 ppm. What is its structure? How would you confirm it spectroscopically?

I initially thought that the structure would be 1,1,1-trichloroethane (shown below) since there will be two different carbon chemical shifts: one bonded to three $$\ce{H}$$ atoms and one $$\ce{C}$$ atom in the 0-50ppm region (corresponding to the 45.1 ppm peak) and another peak for a carbon bonded to three $$\ce{Cl}$$ atoms in the 50-100ppm region (corresponding to the 95.0ppm peak).

Although it considers 1,1,1-trichloroethane, the solutions manual to the book concludes that the correct structure is 1,1,2-trichloroethane (shown below), the other possible structure with formula $$\ce{C2H3Cl3}$$.

However, this compound would have both peaks close to eachother in the 50-100ppm range.

Wouldn't the correct molecule be 1,1,1-trichloroethane, and wouldn't the solutions manual be incorrect? The NMR specs below that I found online corroborate my thinking.

References

Clayden, J., Greeves, N., Warren, S. Organic chemistry, 2nd ed.; Oxford University Press: New York, 2012.

https://www.chemicalbook.com/SpectrumEN_71-55-6_13CNMR.htm

https://spectrabase.com/spectrum/5WUteTf4M4u

• I don't have a copy of the textbook so can't confirm, but the spectra predictions you post are accurate. The wikipedia (infinite in its wisdom) writes of 1,1,1-trichloroethane as a solvent, but not of 1,1,2-TCE. A blooper? – Buck Thorn Dec 15 '18 at 16:09
• Most likely was a blooper on the part of the authors. I just wanted to make sure that my explanations for the two NMRs I found online were correct. – Ethiopius Dec 15 '18 at 16:21
• So probably you should write a very short answer so the Q can be closed – Alchimista Dec 15 '18 at 17:43
• You can find another reliable 13C-NMR on this site: hmdb.ca/spectra/nmr_one_d/3289, which also confirms you are right about 1,1,1-trichloroethane (can find in: pubchem.ncbi.nlm.nih.gov/compound/…). – Mathew Mahindaratne Dec 15 '18 at 22:44
• SDBS: sdbs.db.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi confirms your conclusion. – user55119 Dec 16 '18 at 2:17

I fully agree with your assessment and assume that this is a mistake in the book. I wonder what exactly the authors suggested as spectroscopic verification. I personally would suggest using 1H-NMR as a verification method. In 1,1,1-trichloroethane, only one hydrogen peak should be observed as the three protons of a methyl group are always homotopic. In 1,1,2-trichloroethane, two signals in a $$1:2$$ ratio should be observed as a triplet and dublet, respectively. Depending on what the book suggests as verification, it should be easy to confirm the nomenclature error.