National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 18October 2016
NIST Standard Reference Database 101
IIExperimental data
IIICalculated data
IVData comparisons
VCost comparisons
VIInput and output files
VIITutorials and Units
VIIILinks to other sites
XOlder CCCBDB versions
XIII Vibrations
XIVReaction data
XVEntropy data
XVIBibliographic data
XVIIIon data
XVIIIBad calculations
XIXIndex of properties
XXH-bond dimers

NIST policy on privacy, security, and accessibility.

Please rate our products
© 2013 copyright by the U.S. Secretary of Commerce on behalf of the United States of America. All rights reserved.

The National Institute of Standards and Technology (NIST) is an agency of the U.S. Department of Commerce.

Please send questions, comments, corrections, additions and suggestions to

return to home page

II.A.3. (XII.A.1.)

Listing of experimental geometry data for CH3CCH (propyne)

Rotational Constants (cm-1)

See section I.F.4 to change rotational constant units
5.21000 0.28506 0.28506
Rotational Constants from 1966Herzberg
Calculated rotational constants for CH3CCH (propyne).

Point Group C3v

Internal coordinates

(distances (r) in Å) (angles (a) in degrees) (dihedrals (d) in degrees)
Description Value Connectivity Reference Comment
Atom 1 Atom 2 Atom 3 Atom 4
rCH 1.096 1 5 1973Dun/McK:232 CH3 end
rCH 1.060 3 4 1973Dun/McK:232 CH end
rCC 1.460 1 2 1973Dun/McK:232
rCC 1.207 2 3 1973Dun/McK:232
aHCH 108.28 5 1 6 1966Herzberg
aHCC 110.63 2 1 5 1973Dun/McK:232 from symmetry
picture of propyne

Bond descriptions

Examples: C-C single bond, C=C, double bond, C#C triple bond, C:C aromatic bond
Bond Type Count
H-C 4
C-C 1
C#C 1

Atom x (Å) y (Å) z (Å)
C1 0.0000 0.0000 -1.2455
C2 0.0000 0.0000 0.2135
C3 0.0000 0.0000 1.4195
H4 0.0000 0.0000 2.4755
H5 0.0000 1.0465 -1.6003
H6 0.9063 -0.5232 -1.6003
H7 -0.9063 -0.5232 -1.6003

Atom - Atom Distances (Å)

  C1 C2 C3 H4 H5 H6 H7

Calculated geometries for CH3CCH (propyne).
By selecting the following links, you may be leaving NIST webspace. We have provided these links to other web sites because they may have information that would be of interest to you. No inferences should be drawn on account of other sites being referenced, or not, from this page. There may be other web sites that are more appropriate for your purpose. NIST does not necessarily endorse the views expressed, or concur with the facts presented on these sites. Further, NIST does not endorse any commercial products that may be mentioned on these sites. Please address comments about this page to
squib reference DOI
1966Herzberg Herzberg, G., Electronic spectra and electronic structure of polyatomic molecules,Van Nostrand,New York, 1966  
1973Dun/McK:232 JL Duncan, DC McKean, PD Mallinson, RD McCulloch " Infrared Spectra of CHD2Cl and CHD2CCH and the geometries of Methyl Chloride and Propyne" J. Mol. Spec. 46, 232-239, 1973 10.1016/0022-2852(73)90039-8

Got a better number? Please email us at