The explosive trinitrotoluene (TNT) is made by carrying out three successive nitration reactions on toluene. If these nitrations only occur in the ortho and para positions relative to the methyl group, what is the structure of TNT?

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Welcome everybody. Our next question says, Picric acid or tri nitro phenol. TNP is widely used in explosives and munitions. Prick is formed from phenol to avoid side reactions. Phenol is first sulfurated to form P hydroxy benzene sulfonic acid. This is followed by successive nitration. The sulfuric acid group is then displaced by heating and dilute sulfuric acid and final nitration to produce the desired product. Picric acid. Considering that nitration only occurs in the Ortho and paras positions relative to the hydroxy group predict the structure of picric acid. And we have four different answer choices A through D with four different possible structures. So we'll evaluate those after thinking about this process. So we know we have a final product that's tri nitro phenol. So that would indicate a phenol with three nitro groups. We call it the nitro group is no two. So we have a really long description of what's going on here in a two step process. Sulfonic acid being put on and then replaced. But that's kind of all a little bit distracting because all we have to do is predict the final structure. We know it's got three nitro groups and we have this key information at the end that nitration only occurs in the Ortho and paras positions relative to the hydroxy group. So we already know where those three nitro groups can go. Based on that information, we don't even need to worry about all the multiple steps. So we start with phenol. So we'll draw a phenol molecule here. It's a benzene ring with a hydroxy group on it. And we know that those nitro groups can only be added in the Ortho and pers positions. So which are those positions? We recall, we'll call the carbon where our hydroxy group is attached as number one. So go around and number our carbons. The Ortho positions are the ones next to or adjacent to our group. So Ortho is on carbons two and six than meta positions are two carbons away from the first group that would be on carbons three and five and the para position is 180 degrees away on carbon four. So with that in mind, we know the only locations, there's only three of them where our nitro group could go that would be on carbon two, carbon four are the pair position and carbon 62 and six being the ort of positions. Those are the only three spots available. So if we want to think about our structure, then we know we have our benzene ring with its hydroxy group and then our three nitro groups must go on the hydroxy group is carbon one, our nitro groups go on carbon two, carbon four, oops and carbon six. So with that in mind, let's look at our answer choices and find the one that matches. When we look at choice. A, we have the hydroxy group in the correct place. The two nitro groups on carbons two and six, but on carbon four and the pair position, we have an so three H group. Well, this still reflects the first step in our process. We said the phenols sulfonate to form P hydroxy benzene sulfonic acid and then successive nitration. So this is the point at which you've added this. So three H after its sulfon nation and then you've added two nitro groups, but you haven't done the final step displacing that sulfonic acid group. So choice A is kind of the first stage product not the pic acid. Now, let's look at choice B. Choice B shows our hydroxy group with the three nitro groups at carbons 24 and six. So this indeed matches what we calculated for the structure of picric acid just to be thorough. Let's look at our final two choices. Choice C has no hydroxy group and 1/4 nitro group at carbon one. But we have tri nitro phenol, it's still a phenol. So this is not correct because it's missing its hydroxy group. And then finally, in choice D we have only one nitro group and three hydroxy groups, but this is the reverse of what's supposed to take place. We have tri nitro phenol. So this is not the same molecule. So choice D is not correct. So once again, our comp our problem tells us to predict the structure of picric acid. Given the process that's described, we are supposed to end up with tri nitro phenol. Knowing nitration only occurs in Ortho and paras positions relative to the hydroxy group. So choice B is our correct answer with a hydroxy group on carbon one and nitro groups on carbons 24 and six. See you in the next video.

The explosive trinitrotoluene (TNT) is made by carrying out three successive nitration reactions on toluene. If these nitrations only occur in the ortho and para positions relative to the methyl group, what is the structure of TNT?

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Key Concepts

Nitration Reaction

Ortho and Para Positions

Structure of TNT