return to home page

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

Listing of experimental geometry data for C5H6 (1-Buten-3-yne, 2-methyl-)

Rotational Constants (cm-1)
See section I.F.4 to change rotational constant units
0.31221 0.13388 0.09522
Rotational Constants from NISThydrocarbon
Calculated rotational constants for C5H6 (1-Buten-3-yne, 2-methyl-).

Point Group Cs

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 1.091 9 10 1976Hellwege(II/7) !assumed, end C with =
rCH 1.081 9 11 1976Hellwege(II/7) !assumed, end C with =
rCC 1.336 8 9 1976Hellwege(II/7) !assumed
rCC 1.501 1 8 1976Hellwege(II/7) !assumed, C= to CH3
rCH 1.090 1 2 1976Hellwege(II/7) !assumed, on CH3
rCC 1.445 7 8 1976Hellwege(II/7) between # and =
rCC 1.207 5 7 1976Hellwege(II/7) !assumed
rCH 1.065 5 6 1976Hellwege(II/7) !assumed, on CH
aHCC 121.5 8 9 10 1976Hellwege(II/7) !assumed
aHCC 120.5 8 9 11 1976Hellwege(II/7) !assumed
aCCC 124.3 1 8 9 1976Hellwege(II/7) !assumed, to end C
aCCC 120.3 7 8 9 1976Hellwege(II/7) to C with #
aHCC 111 2 1 8 1976Hellwege(II/7) !assumed, to CH3
picture of 1-Buten-3-yne, 2-methyl-

Bond descriptions
Examples: C-C single bond, C=C, double bond, C#C triple bond, C:C aromatic bond
Bond Type Count
H-C 6
C-C 2
C=C 1
C#C 1

Atom x (Å) y (Å) z (Å)

Atom - Atom Distances (Å)

Calculated geometries for C5H6 (1-Buten-3-yne, 2-methyl-).

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
1976Hellwege(II/7) Hellwege, KH and AM Hellwege (ed.). Landolt-Bornstein: Group II: Atomic and Molecular Physics Volume 7: Structure Data of Free Polyatomic Molecules. Springer-Verlag. Berlin. 1976.  
NISThydrocarbon NIST Hydrocarbon spectral database (  

Got a better number? Please email us at