Triple bonds cause linear configurations
About this video
A short clarification on alkynes. The earlier alkanol example was drawn wrongly: a triple bond between carbons 5 and 6 should be drawn as a straight line, not a bend. Triple bonds force a linear geometry, so the chain runs straight through the alkyne.
You'll be able to
- explain why a triple bond forces a linear configuration
- redraw an alkyne so the chain goes straight through the triple bond
- recognise that an alkyne's triple bond straightens the molecule
Key words
- Alkyne
- A hydrocarbon containing at least one carbon-carbon triple bond.
- Triple bond
- Three shared electron pairs between two atoms, made of one sigma bond and two pi bonds.
- Linear configuration
- An arrangement where atoms sit in a straight line, as at the two ends of a triple bond.
- Alkanol
- An alcohol built on a straight carbon chain, with an -OH group attached.
Transcript
- [Instructor] I wanna do a quick clarification on the video on alcohols. In that video, I gave this example of this alkanol right over here, it has a triple bond between the five and six carbons. And I just wanna clarify that in reality, it would not ever be drawn this way.
That this was an error to actually draw it this way. The way I should have drawn it is this right over here. And you see, the only difference between these two pictures, starting with the one carbon, two carbon, three carbon, everything looks the same. Four carbon attached to the hydroxyl group, everything looks the same.
And then we get to the five carbon, but instead of bending back up, we just keep going straight to the six carbon, that's where we have the triple bond between the five and six carbon, and then we go straight again to the seven carbon that's attached to the two bromo groups.
And then we get to the eighth carbon. And the whole point why this right over here, that this is the correct way to draw it, the correct way to draw it, is that triple bonds, this triple bond right here, it forces a linear configuration. So on both sides of that triple bond, you would go straight out.
So whenever you see an, actually, whenever you see any type of an alkyne drawn, the triple bonds should essentially straighten out. It should straighten out the molecule.
Video © Khan Academy, used under CC BY-NC-SA. Watch on Khan Academy. Puzzicle is not affiliated with Khan Academy.