Which alkene contains a tetrasubstituted double bond

Please wait while we load your content Something went wrong. Try again? Cited by. Download options Please wait Article type Review Article. Submitted 05 Sep Accepted 03 Nov First published 06 Nov Download Citation. So here we have three examples of disubstituted alkenes. Let's look at this one down here and let's name it. So find our longest carbon chain that includes our double bond, and I wanna give the lowest number possible to our double bond, so we're gonna start right here at carbon one, this is carbon two, and this is carbon three.

So three carbon alkene is called propene, and we have a methyl group coming off carbon two, so this would be 2-Methylpropene. In terms of which type of disubstituted alkene this is, let's go ahead and draw in our hydrogens so it's a little bit easier to see.

So, for this carbon, there are two hydrogens bonded to it, and then for the carbon on the left, it has a methyl group and another methyl group. So, two R groups that happen to be the same. So that's this example of a disubstituted alkene, where both of our R groups are bonded to one carbon. Now let's look at a trisubstituted alkene. So, we have three R groups. R, R prime, and R double prime. And again, R, R prime, and R double prime might be the same, or they might be different.

So here's an example of a trisubstituted alkene. Let me go ahead and draw in the hydrogen on this carbon, so it's easier to see that we have three R groups bonded to the double bonds. If I want to name it, I need to find the longest carbon chain that includes my double bond, so this would be carbon one, this would be carbon two, three, four, and five.

So a five carbon alkene is called pentene, so let me write that in here, and our double bond starts at carbon two, so this would be 2-Pentene. And finally, I have a methyl group coming off of carbon two. So, to complete the name, I need 2-Methyl, so 2-MethylPentene would be the name for this trisubstituted alkene. Next, let's look at a tetrasubstituted alkene.

So R, R prime, R double prime, and R triple prime. This molecule is actually tetrasubstituted. If we find our double bond, so this carbon and this carbon, so this top carbon here, actually, let's go ahead and name it first, and then we'll look at why it's a tetrasubstituted alkene. You should review the priority system. It is also illustrated below in some examples. Vinylidene molecules are not common industrially and will not be discussed further.

As illustrated in Figure 1, cis isomers have their hydrogens on the same side of the double bond, while trans isomers have their hydrogens diagonally across from each other. Many food labels these days contain statements about how much cis and trans fats a product contains. As we will see below, cis and trans isomers have different IR spectra, which is why IR spectroscopy can be used to distinguish and quantitate these fats in samples. When an alkene contains three R-groups and one hydrogen it is called a trisubstituted alkene.

These have no structural isomers. In my opinion, the most industrially important alkenes are the vinyl, cis-, trans-, and trisubstituted varieties. As a result, our discussion below focuses on these types of molecules. We shall discover that we can distinguish all six types of alkenes from each other using IR spectroscopy.

In a previous column 6 , we saw that the saturated carbon containing functional groups methyl CH 3 and methylene CH 2 both have C-H stretches below Another type of saturated carbon, the methine group, which consists of a carbon atom with three C-C bonds and one C-H bond, also has a C-H stretching peak below methine groups will be discussed in a future column on branched alkanes.

In general, saturated carbons have C-H stretching peaks below From our discussion of aromatic rings we found that these unsaturated molecules have C-H stretches above 2. Alkenes and alkynes , unsaturated molecules with carbon—carbon triple bonds, also have C-H stretches above So, in general, we can say that molecules with saturated carbons have C-H stretches below , while molecules with unsaturated carbons have C-H stretches above These ideas are summarized in Table I.

I have stated in previous columns that all of the peak ranges I present have exceptions, and that there are no absolute rules when it comes to interpreting IR spectra. Although the rules in Table I have known exceptions, they are few and Table I is an excellent tool to use when interpreting IR spectra. Determining whether the C-H stretches in a spectrum are above or below is quick and easy, and it should be one of the first pieces of information you extract from a spectrum.

Recall that methyl and methylene groups have specific C-H stretching peaks that can be used to distinguish them from each other 6. Unfortunately, this situation is generally not the case for unsaturated carbons. Both aromatic rings and alkenes typically have their C-H stretches between and