L-Cysteine

• Formula: C₃H₇NO₂S
• Molecular weight: 121.158
• IUPAC Standard InChI: InChI=1S/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)/t2-/m1/s1 Copy

  
• IUPAC Standard InChIKey: XUJNEKJLAYXESH-UWTATZPHSA-N Copy
• CAS Registry Number: 52-90-4
• Chemical structure:
  This structure is also available as a 2d Mol file or as a computed 3d SD file
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• Stereoisomers:
  • dl-Cysteine
• Other names: Cysteine, L-; β-Mercaptoalanine; Cystein; Cysteine; Half-cystine; L-(+)-Cysteine; L-Alanine, 3-mercapto-; NSC-8746; Propanoic Acid, 2-amino-3-mercapto-, (R)-; Thioserine; (R)-2-Amino-3-mercaptopropanoic acid; α-Amino-β-thiolpropionic acid; (R)-Cysteine; 2-Amino-3-mercaptopropionic acid; L-Cys
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Condensed phase thermochemistry data
  • Reaction thermochemistry data
  • Gas phase ion energetics data
  • Mass spectrum (electron ionization)
  • UV/Visible spectrum
  • References
  • Notes
• Data at other public NIST sites:
  • X-ray Photoelectron Spectroscopy Database, version 5.0
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Condensed phase thermochemistry data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled as indicated in comments:
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
DH - Eugene S. Domalski and Elizabeth D. Hearing

Constant pressure heat capacity of solid

Reaction thermochemistry data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled by: John E. Bartmess

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. A general reaction search form is also available. Future versions of this site may rely on reaction search pages in place of the enumerated reaction displays seen below.

Individual Reactions

C₃H₆NO₂S^- +  =

By formula: C₃H₆NO₂S^- + H⁺ = C₃H₇NO₂S

Gas phase ion energetics data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias

Data compiled as indicated in comments:
B - John E. Bartmess

De-protonation reactions

C₃H₆NO₂S^- +  =

By formula: C₃H₆NO₂S^- + H⁺ = C₃H₇NO₂S

Mass spectrum (electron ionization)

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director

Spectrum

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Additional Data

UV/Visible spectrum

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled by: Victor Talrose, Alexander N. Yermakov, Alexy A. Usov, Antonina A. Goncharova, Axlexander N. Leskin, Natalia A. Messineva, Natalia V. Trusova, Margarita V. Efimkina

Spectrum

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Additional Data

References

Go To: Top, Condensed phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, Mass spectrum (electron ionization), UV/Visible spectrum, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Sabbah and Minadakis, 1981
Sabbah, R.; Minadakis, C., Thermodynamique de substances soufrees. II. Etude thermochimique de la l-cysteine et de la l-methionine, Thermochim. Acta, 1981, 43, 269-277. [all data]

Becker and Roth, 1934
Becker, G.; Roth, W.A., Zur bestimmung der verbrennungswarme von organischen schwefelverbindunge, Z. Phys. Chem., 1934, 169, 287-296. [all data]

Sunner, 1946
Sunner, S., Determination of combustion heats of organo-sulphur compounds, Svensk. Kim. Tidr., 1946, 58, 71-81. [all data]

Cox and Pilcher, 1970
Cox, J.D.; Pilcher, G., Thermochemistry of Organic and Organometallic Compounds, Academic Press, New York, 1970, 1-636. [all data]

Huffman and Ellis, 1935
Huffman, H.M.; Ellis, E.L., Thermal Data. II. The heats of combustion of l-cysteine, of l-cystine, β-thiolactic acid and β,β'-dithiodilactic acid, J. Am. Chem. Soc., 1935, 57, 41-46. [all data]

Huffman and Ellis, 1935, 2
Huffman, H.M.; Ellis, E.L., Thermal data. III. The heat capacities, entropies and free energies of four organic compounds containing sulfur, J. Am. Chem. Soc., 1935, 57, 46-48. [all data]

Jones, Bernier, et al., 2007
Jones, C.M.; Bernier, M.; Carson, E.; Colyer, K.E.; Metz, R.; Pawlow, A.; Wischow, E.D.; Webb, I.; Andriole, E.J.; Poutsma, J.C., Gas-phase Acities of the 20 Protein Amino Acids, Int. J. Mass Spectrom., 2007, 267, 1-3, 54-62, https://doi.org/10.1016/j.ijms.2007.02.018 . [all data]

Tian, Pawlow, et al., 2007
Tian, Z.X.; Pawlow, A.; Poutsma, J.C.; Kass, S.R., Are carboxyl groups the most acidic sites in amino acids? Gas-phase acidity, H/D exchange experiments, and computations on cysteine and its conjugate base, J. Am. Chem. Soc., 2007, 129, 17, 5403-5407, https://doi.org/10.1021/ja0666194 . [all data]

DeBlase, Kass, et al., 2014
DeBlase, A.F.; Kass, S.R.; Johnson, M.A., On the character of the cyclic ionic H-bond in cryogenically cooled deprotonated cysteine, Phys. Chem. Chem. Phys., 2014, 16, 10, 4569-4575, https://doi.org/10.1039/c3cp54117g . [all data]

O'Hair, Bowie, et al., 1992
O'Hair, R.J.; Bowie, J.H.; Gronert, S., Gas Phase Acidity of the alpha-Amino Acids, Int. J. Mass Spectrom. Ion Proc., 1992, 117, 23, https://doi.org/10.1016/0168-1176(92)80083-D . [all data]

Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G., Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update, J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018 . [all data]

Johnson, 1971
Johnson, E.A., UV atlas of organic compounds, 1971, 5, J2/3. [all data]

Notes

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• Symbols used in this document:
  

  Cp,solid	Constant pressure heat capacity of solid
  S°solid,1 bar	Entropy of solid at standard conditions (1 bar)
  ΔcH°solid	Enthalpy of combustion of solid at standard conditions
  ΔfH°solid	Enthalpy of formation of solid at standard conditions
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions

• Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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