# Why are triple covalent carbon to carbon bonds drawn linearly in skeletal structure? [duplicate]

In the link see that cyclic C-C structure with a triple covalent bond is drawn with an angle, probably the only way to draw it but why is it drawn linearly in non-cyclic and not like single or double bond? I am wondering about the reason for this not that its a convention.

Alkyne Wikipedia

• A triple bond is drawn this way because it is this way. There is nothing conventional about it. May 16 '19 at 10:14
• I'm afraid I don't quite follow. Are you asking why $\ce{-C#C-}$ group is linear, or why no stereospecific descriptors such as Cram bonds were used to depict structure f (cycloheptyne)? May 16 '19 at 10:20
• I am asking why the 180degree angle that is drawn in carbon to carbon skeletal structure and not the 120 or what is it in single and double bonds. I saw in many yt videos and other websites that this is the way to draw triple bonds but why is it? Is it the actual geometry of the compunds? If so why is that? Do you know of any source that could explain to me the why? In the cyclic compund the structure has an angle. I dont understand why in non-cyclic it is a 180 degree May 16 '19 at 10:40
• @ŽanSpehonja The carbon atoms in $\ce{-C#C-}$ are linked by one σ- and two π-bonds, the maximum electron density of which is located in two mutually perpendicular planes. Two intersecting planes form a straight line. May 16 '19 at 11:33
• The structure (f) is therefore not very accurately drawn because the molecule will be highly strained, the $\ce{-C\equiv C-}$ bond wanting to be straight and the others at 109 degrees. May 16 '19 at 13:25

The −C≡C− is normally drawn as linear about each C atom as that is what is found in nature for most alkyne x-ray crystal structures. We can use hybridization theory to explain this as the C atoms would be expected to adopt an sp hybridization, which gives two hybrid orbitals along the axis of the p orbital hybridized with the s to make the sp hybrids:

https://courses.lumenlearning.com/introchem/chapter/sp-hybridization/

These orbitals will then overlap with orbitals on adjacent atoms to make two sigma bonds in a linear arrangement about each C atom, giving alkynes their overall linear shape: https://chem-is-you.blogspot.com/2012/09/organic-chemistry-for-level-structure.html

Cycloalkynes tend to be strained molecules as the ideal bond angles of $$180^o$$ about the alkyne C atoms are not consistent with a small cyclic molecule. This causes cycloalkynes with less than 10 C atoms to have measurable strain and the strain increases as the ring gets smaller:

https://en.wikipedia.org/wiki/Cycloalkyne

Chemical drawing programs will tend to keep the general shape of a cyclic structure (a heptagon in the case of molecule f) and just add the triple bond, but it does do a good job of indicating to us that the molecule will suffer from this strain as it naturally tends to deviate the angles away from $$180^o$$!

• Upvoted because refers to strain. May 17 '19 at 10:11

Triple bond in carbon means that the carbon atom is sp hybridized. sp hybridized carbon has the two bonded groups at 180 to each other. Therefore it is displayed linearly which is closest to the actual structure. Single and double bonds are at an angle of nearly 109.5 and 120 degree therefore are not drawn linearly.