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NIST Organic Thermochemistry Archive (NOTA)

H.Y. Afeefy, J.F. Liebman, and S.E. Stein


  1. Overview
  2. Sources of Data
  3. Data Reporting
  4. Data Reliability


The Chemical and Physical Properties Division at NIST is engaged in an effort to collect, organize and disseminate all available enthalpies of reaction and formation of organic compounds. This is the first release of these data, covering the literature up to June 1996. The immediate objective of this effort is to accurately record these data, even if derived from indirect measurements such as appearance potentials and radical recombination energies. A longer range objective is to evaluate and when possible correct errors in the original data as well as to add additional relevant data, especially enthalpies of vaporization and sublimation. These data will also serve as a basis for improving the accuracy and coverage of thermochemical estimation methods.

Sources of Data

The hunt for relevant publications began at three starting points: Chemical Abstracts, books with reference data, and an early NIST collection of abstracts ("yellow cards"). Except where noted, all data were re-abstracted from original papers, so recorded values should exactly match reported values. After extracting relevant data from the original sources, all relevant references to papers not already abstracted were examined and, if new data were discovered, data from these new papers were abstracted and a citation for this new reference was added to our bibliography. This process continued until no new relevant references were found. This reference-to-reference exploration process often led to data not recorded in existing compilations.

Chemical Abstracts: This was the first stage of the collection process. Relevant subject indexes back to 1970 were examined under a range of relevant subject topics. Based on titles, individual abstracts were then examined, and if the reference was thought to contain new data, complete papers were located and abstracted. If original papers were unavailable at NIST and through Interlibrary Loan, data were taken from the abstract itself and noted in a comments field.

Books with reference data: The principal reference collections were:

  1. Thermochemical Data of Organic Compounds by J.B. Pedley, R.D. Naylor, and S.P. Kirby, Chapman and Hall, New York, 1986
  2. Thermochemistry of Organic and Organometallic Compounds by J.D. Cox and G. Pilcher, Academic Press, New York, 1970
  3. The Chemical Thermodynamics of Organic Compounds by D.R. Stull, E.F. Westrum and G.C. Sinke, John Wiley and Sons, New York, 1969

Any significant differences between original values and values reported in reference books are noted in the comments.

"Yellow Cards": Several thousand index cards containing abstracts of papers dating from 1852 to 1969 had earlier been archived in the NIST Thermochemistry Data Center. Values reported in these abstracts guided the extraction of data from the original paper. Papers before 1946 have not yet been processed.

Data Reporting

In cases where a single measurement was reported in several papers, only the original is reported. If the value was corrected in a later work, this is noted in the comments. Significant work remains in eliminating multiple entries originating from a single determination.

Efforts were made to correct all mathematical mistakes in the derivation of enthalpy of formation from measured data. Any exceptional features of a reported value is noted in the comments. Values for cases where there is an unexplained large discrepancy between a reported value and other seemingly reliable value are given in brackets.

Data Reliability

No data reported in this archive have been evaluated by the authors at NIST. Our present objective is simply to accurately record the original data. Moreover, the present version is not yet complete and inconsistencies are still being discovered and corrected.