(a) Outline the syntheses indicated in Solved Problem 18-2, be...

Question

(a) Outline the syntheses indicated in Solved Problem 18-2, beginning with aldehydes and alkyl halides.

(b) Both of these syntheses of 1-phenylbuta-1,3-diene form the central double bond. Show how you would synthesize this target molecule by forming the terminal double bond.

Accepted Answer

Hey everyone and welcome back in today's video, we are going to solve the following problem. Number one outlined. The synthesis is shown below using alcohol and alcohol. Hey lights as your starting materials and number to show how to make pan to 13 dying via the formation of the terminal double bond. We're going to start this problem by looking at the final structure that we're synthesizing which would come from two different pathways. The first pathway has an AL to hide and a prosperous Allied. Right. So we have our Allied because we have phosphorus double bonded to carbon that has three final substitue ints And similarly here we have our phosphorus Allied and our Aldo hides. We have our elder hides. We have two carbon compounds reacting with two allies in each case. Right? One elder Hyde which with one Allied and we may recall that this is the Wittig reaction because this is the Wittig reaction. We understand that if we combine these two together we will form the final product. Notice that if you essentially get rid of oxygen and get rid of try final falsifying part, you're going to merge this, these two fragments or basically these two partial double bonds into one and you will get your final product. So the only thing that we want to think about is just the formation of the Allied itself. Now let's think about the formation of each Allied. Remember that Allied's can undergo resonance. Right, So we can break this pipe on and transfer our electrons onto carbon and same thing here. And basically if we think about the residents structure that would correspond to the following phosphorus try final fosse fine. Right. And then we have our single bond 123 carbon atoms. We're going to add 123. We're going to add our double bond phosphorus would have a positive charge. Carbon would have a negative charge. And this fragment comes from the D protein nation. Stop. Right. We can say that we definitely want to deep protein ate the other structure where we have two hydrogen atoms here instead of one. So we're going to draw PH three p. Now suppose that here you actually have two hydrogen atoms and now we are essentially going to use normal bees. A lithium here our strong base to D protein it the structure and form the Allied. But now the question is how to arrive at this one. Remember that we want to make sure that we are starting with a good leaving group so we can replace our fragment with a good leaving groups such as roaming and if we see so we get the following starting material that's our alcohol. Hey light we just want to treat it with try fennel pass fine and that's basically our idea. We can use this model to each of our reactions. So let's start swimming in the first part. We understand that we have our alcohol. Hey light we need to treat it with Trifonov costs fine to produce our fragment. Then we treat it normal Visa lithium two D. Protein ate it and form our allied. That allied is resonance stabilized and then we have our two plus two psycho edition and reverse cycle edition between the two structures to form our final product. And we can use this model for each of these. So let's start with the first part. For the first part we already know which our L kill. Hey light is actually it's vinyl. Hey light right? Because we have our pi bon. So this is our starting material and as we said we need to perform three reactions First of all. Number one addition of try fennel fast fine which will allow us to replace our bromo substitute print with try fennel foss fin. So that bP pH three. The next reaction is addition of normal beth a lithium we are going to D protein it the structure. And basically get our Allied and number three we're going to use the alga hide shown. And if you remember this is ethanol. So let's draw ethanol and that will be it. This is how we get our final products shown. Now for the second pathway we need to identify our L kill Hey light and that'll be it. Now. What will be the fastest way to do that? We're going back to our allied as we said before we are going to replace our PPH three with a good leaving group. Right? So essentially we want to make sure that here we have our bromo substitution it's not technically correct to cross that. But you may easily visualize what's happening here. So imagine that we're crossing it out. We're changing this with our bromo substitution, breaking our pi bond and essentially adding one hydrogen here. Right? Because we are going to d protein ate it at the weigh in. So our alcohol. Hey light here would correspond to promos a notice that we have 12 carbon atoms. Right? And then we're going to replace PP three with our bromo substitution. So that would be it. And then we have our Aldo height. So let's draw the required steps. We're going to start with bromo ethane. Two carbon atoms responded to booming. And we are going to perform exactly the same steps. These steps are as follows. Step number one addition of tri fennel fast fine Number two addition of normal bees. A lithium number three treatment of the allied with our Aldo hide. So that Aldo hide was essentially our carbon in group. We control hydrogen. And then on the other hand we have our carbon and then we have our double bond. So let's see if that's correct. We have Yeah, that's correct. Basically we have our single bond between that carbon and this carbon and then we have our double bond. So that makes sense. And once again this would give us our product. Remember that First of all we are replacing brimming with try final foss fine We're d protein eating it at that position to form our allied. And when we have our allies, we have our reverse we have our two plus two psycho edition, followed by the reverse cycle edition. So this will be our two pathways for number one. We may label these as our final answers and now we are ready to move on to the second part. In the second part. The problem states that we actually want to break this bond instead. So what kind of materials we can use from here. So, first of all, if we break it that way, we can form an alga hide and our allied. So now one of the ways is to suppose that the right hand side corresponds to your allied. And to do that. We're just going to draw that ph three p fragment bonded to that carbon B. A double bond. Okay, so that would be your ally. And then we have to think about the remaining part of the structure. So we are going to draw everything on the left. But now we're going to add oxygen here. So B. G. So we are going to start with this double bond. We're going to add oxygen immediately over here. Then draw another double bond over here. And then we noticed clearly that we also have our metal group Bonnett said. So these could be our reagents. And now another case is to use the right hand side fragment. Let's keep in mind that here we are going to use two hydrogen atoms for this allied right? There are no two method groups. We said that we are signing this part to our Allied. And from the other perspective if we suppose that the right hand side corresponds to our carbon compound, we can see that another pathway is actually to use there's double bond with two hydrogen atoms and make it an AL to hide. So the remaining part would correspond to our allied meaning we can just throw our double bond Here on our double bond. We are going to assign phosphorus with 33 final rings. And now essentially we're going to redraw everything else. Okay, so we have our ally. This is our possibility for the Allied and our al to hide. We have two possible ways to do that. And just as we did it before, we just have to think how to form these allies from a corresponding L kill Hey lights. So for this one, as we said before we are going to get rid of try fennel falsifying part and we're going to replace it with our bromo group And that would be it right. We are going to break our double bond and add an additional proton. So notice how you only have one carbon atom. If you add an additional hygiene, you get your metal group and metal group is going to be bonded to blooming. So one of the ways to get it is to use metal bromide or basically bromo methane. Right? We can say that would be our CH three B. R. We can get it from C. Three B. R. And thinking about this Allied we are going to redraw everything so our metal group our double bond going down. We will not have this double bond anymore. We will actually have a single bond monetary booming. And as we said before we are going to use these L. Kill Hayley's and this I'll kill hey light and this vinyl hey light to form our allies. Using these three basic steps actually two basic steps number one and number two we will get our allies which will react with the given carbon compounds. So we are ready to write down our summary or number two we said that the first alcohol hey light that we're using is metal bromide. So we're going to use C. Three br. Okay So this or basically let's just write it down as c. three p. R. There is no necessity to show the actual bonding so we can just draw it as ch three B. Are now bromo methane. First of all must produce our allied and we're going to use steps number one and two addition of try fennel sauce fine followed by the addition of normal Visa lithium. This is how we get our allied and now we said that the remaining carbonell compound that we have is the following Aldo hide. We just want to have our metal group bonded to that sp two hybridized carbon atom and then we are ready to throw our elder Hyde group. So this is one pathway to get our product. And the second pathway was to use a different alcohol highlight which was actually our vinyl. Hey lights, we're going to draw our metal group double bond CH two bonded to roaming and once again we're going to beat exactly same steps. We're just going to change reaction number three because we're using a different carbon metal compound but steps number one and to remain the same. So we're going to use try fennel past fine normal B cell lithium Number three. Which carbonell compound did we choose? So that was formaldehyde. Right? We have each C. H. O. If you look back to our problem, this is formaldehyde, right? This is exactly same carbonell compound that we rode down here. So this is our second pathway, let's label this is our final answer two part number two. And we can also state that this would produce the required product based on what we see here. We may conclude that the final answers the multiple choice question is a However, if you have any questions don't hesitate to leave a comment down below. Thank you for watching

(a) Outline the syntheses indicated in Solved Problem 18-2, beginning with aldehydes and alkyl halides.
(b) Both of these syntheses of 1-phenylbuta-1,3-diene form the central double bond. Show how you would synthesize this target molecule by forming the terminal double bond.

Key Concepts

Aldehydes and Alkyl Halides

Formation of Double Bonds

Phosphorus Ylides

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