Problem 30 in Chapter 3 asked you to give the structures of all alkenes with molecular formula C

step 1 So here we are going to make some C6 H12 alken isomers. So if we just start off with a completel

Problem 30 in Chapter 3 asked you to give the structures of...

Key Concepts

Hyperconjugation

Hyperconjugation refers to the delocalization of electrons via sigma bonds from adjacent alkyl groups into the empty or partially filled p-orbitals of the double bond. This electron donation stabilizes the double bond and is a key factor in the increased stability of more substituted alkenes.

Heat of Hydrogenation

Heat of hydrogenation is an experimental measure used to assess alkene stability. More stable alkenes release less energy upon hydrogenation than less stable ones, making a lower heat of hydrogenation indicative of a more substituted and/or trans alkene. This concept provides a quantitative way to compare the relative energies of various alkenes.

Degree of Alkene Substitution

The stability of alkenes greatly depends on how many alkyl groups are attached to the carbon atoms of the double bond. More alkyl substituents lead to increased electron donation through hyperconjugation, which stabilizes the alkene by delocalizing electron density into the electron?deficient double bond. In general, tetra-substituted alkenes are more stable than tri-, di-, mono-, and unsubstituted alkenes.

Geometric Isomerism (cis-trans Isomerism)

In alkenes, the spatial arrangement of substituents around the double bond results in cis and trans isomers. Trans isomers are typically more stable than cis isomers because the substituents in trans configurations are farther apart, reducing steric hindrance and repulsive interactions between bulky groups.

Transcript

00:01 So here we are going to make some c6 h12 alken isomers.

00:10 So if we just start off with a completely linear head scene, we can have a level bond at this position, at the two position, and then again at the three position.

00:27 If we then move on to the four position, we've basically recreated the two positions.

00:33 It's only these three positions here.

00:37 And basically for each compound we have, we do have just a trans, but now we will simply just consider either the trans version.

00:50 Okay, done with that, we can also basically form, instead of a hexine, we can now do a pencine.

01:03 And then also have methyl substituent there okay so let's say my whole substituent we can have double bond basically be in all these various positions okay i guess it's a bit more flexibility there okay and still sticking to the pen team let's say we move it the double bond down here we can form a lot of just moving the double bond and moving that methyl we can form even larger amount okay so you can do the two methyl and the three methyl the four methyl will then be the same as a two methyl and the one in five methyl will basically be the same thing as a hexene okay so then with that we've exhausted that one and we can move on to basically some dimethyls here so to get into the dimethyls we need to move to the four position and we can have this kind of a dimethyl job there then draw it like this you can have an exo type a terminal type dimethyl you have dimethyl on the same carbon in this beauty what else? what else? and then, i believe we have listed out all of the possible c6 h -12s.

03:05 Al -kines.

03:08 Okay, so then with that, we are to consider the most stable and the least stable.

03:12 So the most stable would be the pfeclos would be the one where the all -keland.

03:23 Is the most amount of, you know, just the highest substitution.

03:30 So we're looking at this guy here, where there is no h, there's no sb2 carbon hydrogen.

03:40 This al -qeen is fully basically substituted there.

03:44 So that would be the most stable, ice conjugation.

03:48 Then the least stable one would be one with, you know, that does not have, a kind of conjugation.

04:00 It's the less conjugation.

04:02 So the ones with the primary.

04:05 Yep.

04:09 Okay.

04:11 So we can call right there.

04:15 This has the highest stability...

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