The following alkenes can be prepared by dehydration of an appropriate alcohol. Show the structure of the alcohol in each case that would provide the alkene shown as the major product.
e. 1,4-Pentadiene

Question

The following alkenes can be prepared by dehydration of an appropriate alcohol. Show the structure of the alcohol in each case that would provide the alkene shown as the major product.

e. 1,4-Pentadiene

Accepted Answer

Welcome back. Here's our next problem, identify the structure of the alcohol that would provide 34 dimethyl hea 15 dying as the major product. And we have three potential structures labeled 12 and three with the alcohol groups on different carbons. And answer choices of a one only B, three, only C one and two or D one and three. Well, our starting point of course is to draw the structure, the name that we're given as the major product. And then we can think about which alcohol would give this. So we have a Hexad dyne. So we have a six carbon chain. So we'll start by drawing that in 23456, double check. We have the right number 123456, we have two double bonds since it's a dying at carbon one and carbon five. So the double bonds are at the beginning and end of the molecule connected to the two terminal carbons that will be important. And then we have methyl groups on carbons three and four. So we'll draw them in. So let's think about which alcohols would yield these double bonds. Well, we can recall that in a dehydration reaction, we have our cc double bonded and we eliminate the oh group from one carbon and the hydrogen from an adjacent Carmen. So with that in mind, let's look over at our molecule that we know is the major product. So we know that when we look at this double bond, we could have had the alcohol group originally on either end of it. So either carbon one or carbon two for the uh 12, double bond, and then either carbon five or carbon six for the 56 double bond. However, when we think about where this would be, we need to remember Zef's rule which tells us that the major product in a dehydration like this will be the more substituted alkene since it will be more stable. So what would happen if our alcohol group was on carbon two or carbon five? Well, let's draw in that circumstance if that alcohol group was on carbon two, for instance, there could be two possible Alkins formed, either the one we see in the molecule we're supposed to look at or a double bond formed between carbons two and three, eliminating the hydrogen on carbon three. In that case, the more stable alkene would be the 23 alkene that I'm drawing here in red because of the methyl group on carbon three. So again, that means if the alcohol group was on C two, carbon two or carbon five, C five the major product would be the one with the methyl, substituted double bond. So it would not be the product we're given in this answer choice. So that eliminates choice two where we have the oh group on carbon two and carbon five. And it also eliminates problem three where we see we have our alcohol group on carbon three and carbon four. Again, that would give an internal double bond rather than the terminal double bonds that we see on the product that we desire. So we need our alcohol groups to have been as in number one on the terminal carbons. So that there's only one choice for the location of the double bond since there are no substituents on those carmens. So our answer choice here then is choice a one only for the possible structure of the alcohol that would provide 34 dimethyl hea 15 dying as the major product. See you in the next video.

The following alkenes can be prepared by dehydration of an appropriate alcohol. Show the structure of the alcohol in each case that would provide the alkene shown as the major product.
e. 1,4-Pentadiene

Verified video answer for a similar problem:

Key Concepts

Dehydration Reaction

Zaitsev's Rule

Structure of Alkenes

The following alkenes can be prepared by dehydration of an appropriate alcohol. Show the structure of the alcohol in each case that would provide the alkene shown as the major product.e. 1,4-Pentadiene

Verified video answer for a similar problem:

Key Concepts

Dehydration Reaction

Zaitsev's Rule

Structure of Alkenes

The following alkenes can be prepared by dehydration of an appropriate alcohol. Show the structure of the alcohol in each case that would provide the alkene shown as the major product.
e. 1,4-Pentadiene