A student was given the structural formulas of several compoun...

Question

A student was given the structural formulas of several compounds and was asked to give them systematic names. How many did the student name correctly? Correct those that are misnamed.

a. 4-bromo-3-pentanol

b. 2,2-dimethyl-4-ethylheptane

Accepted Answer

Welcome back everyone. How many of the following systematic names are correct, correct. Those that are misnamed number 14, Chloro Pen 30 and number 2223, triathalon. We can start with the first name and our goal is to draw the structure based on the given name. So first of all, we want to identify the parent, which is 30 and that means we have fentaNYL as an alcohol, which will have a total of five carbon atoms in the parent chain. Now 30 tells us that we have an alcohol group O H bonded to carbon number three. So we can essentially enumerate our parent the way we wish from left to right or right to left. It doesn't really matter and we will use it for reference for the next structure. We are just going to eliminate those coefficients so that we can actually see the bonding pattern. Now, based on the name, the alcohol group is bonded to carbon number three. So we're going to add our hydroxyl substituent and also bonded to carbon. Number four, there's a Chloro substituent. Now we want to check if that name is correct whenever we have an alcohol, it gets priority, right. So we want to make sure that we minimize the coefficient for the alcohol group. If we go from left to right, the alcohol group appears bonded to carbon number three. But if we go from right to left, you would have 1 to 3, that's still carbon number three. So so far so good in both cases, we will have 30 in our name. Now, of course, our parent is, so we're going to say Tencent, we o right, because the longest carbon chain corresponds to a total of five carbon atoms. And now we simply want to make sure that we enumerate our parent from the side that allows us to minimize the coefficients for our substitutions. So instead of going from left to right, we will go from right to left because that would give us a lower coefficient for the chloral substituent. Instead of having it bonded to carbon number four, we will now see it bonded to carbon number two. And that means we can correct our name to two Chloro pan 30, which will be appropriate. So let's go ahead and add that to Chloro three. Oh That would be the correct name. And we can say that the first structure was misnamed, well done. So let's go ahead and label the correct name for the structure. Now, we are ready to continue and take a look at the second structure. So we are always starting with our parent and we notice that we have Hexane. So Hexing corresponds to a six member chain. So first of all, we're drawing our six member chain, we're going to duplicate it so that we can clearly see which carbon corresponds to which position. So we can enumerate it from left to right. And let's take a look at our name. So 223 tri methyl, that means positions two and three, they have a total of three methyl substations. Two of them belong to carbon number two. So we're going to add two methyl substi and now the third one belongs to carbon number three. OK. Well done. We are done with our methyl substitutions and then bonded to carbon number four, we will have an ethyl substituent. So let's draw an ethel substituent. Now, we simply wish to check if our parent chain indeed consists of six carbon atoms, we can go from left to right. And we will notice that we have 1234. And now it doesn't matter if we go up or down, we will still have two additional carbon atoms. So indeed, we first will check our structure and we determine that the structure must be hexane because that would be the longest continuous carbon chain. Now, let's think about the substitutions. If we enumerate our parent from left to right, we will end up with 223 triethyl four ethyl hexane. That that's OK. But if we go from right to left. And if we change our numbering system, let's see, in green, we would have 123456. And immediately we noticed that we don't want to use that because we will increase the coefficient, the ethyl group will be bonded to carbon number three, that's lower than four, that's fine. But if we look at the methyl groups, they will be bonded to carbons 45 and five. So instead of having 223, we will have four, five and five and the sum of the coefficients. In this case, if we use 455 and for the group, we will use three, the total sum will be greater than the sum of the coefficients in the given name. Meaning we actually want to leave our numbering system based on the original assignment in blue. However, there's an issue with the name. We definitely agree that the ethyl substation responded to carbon number four. And we also agree that we have 223 tri methyl. But we have to keep in mind that whenever we name our structure, we arrange our substitutions based on the alphabetical priority. So L will be our first substituent followed by the methyl one. We drop our prefix and we only compare the letters that actually define our substituent. So we should start our name by adding four F O based on the alphabetical priority followed by the methyl substituent. We have three of them. So we're going to say 223 because they're bonded to carbons two, two and three, right? And then we're saying tri methyl because we have three methyl substitutions bond bonded to those carbon atoms. And we finish our name with Hexane, which is our parent. So that would be the correct name. And the mistake that we had in this name was made because we didn't arrange the substitutions in terms of the alphabetical priority. So the actual names would be for number one, there was a mistake, we said that the actual name is two Chloro Pen and 30. And for the second one, the correct name would be 4223 Trime Hexane. Thank you for watching and I hope to see you in the next video.

A student was given the structural formulas of several compounds and was asked to give them systematic names. How many did the student name correctly? Correct those that are misnamed.
a. 4-bromo-3-pentanol
b. 2,2-dimethyl-4-ethylheptane

Key Concepts

IUPAC Nomenclature

Functional Groups

Chain Length and Substituents

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