naming complex substituents that's going to be the topic for this lesson in my organic chemistry playlist now we just went through uh an entire lesson on naming alkanes we went through all the little rules and numbering the longest continuous chain and how to end the substituents to get the proper chain locators and which way to number it and all this stuff but one thing we actually haven't covered though is what if you don't have simple substituents like simple methyl ethyl propyl butyl so type groups and stuff like that what if we have what are called complex substituents well it turns out there's going to be two ways to name them so some of them have common names and then there's always going to be a systematic name available and that's what's going to be covered in this lesson now if this is your first time joining me welcome to chad's prep my name is chad and my goal is simply to make science both understandable and even enjoyable now this is my brand new organic chemistry playlist i'll be releasing these lessons weekly throughout the 2020-21 school year so if you don't want to miss one subscribe to the channel click the bell notifications you'll be notified every time i post a new video all right so naming complex substituents here and we'll start off with a simple substituent and then we'll turn it into a complex one to make this harder now if we look at our parent chain here we can definitely identify the longest continuous chain pretty easily that is our parent chain and if we were going to number these things to make sure that that substituent got the lowest possible number it would be located one two three four five six from this direction or one two three four five six seven so we'd number it one two three four five six and i'll just number three the rest here and this would be some form of dodicane here so in this case this would just be a simple substituent just be an ethyl group two carbons no not too bad and it'd be six ethyl doticane now what if we make this one carbon longer well now that's just going to be six propyl dota cane it's still just a simple substituent so however if all of a sudden i do that we have a problem so because it's not a butyl group a butyl group would have added that carbon just one carbon long it would have been a straight substituent straight chain we'll say so however by making it branched that's what actually makes it a complex substituent and none of the names we've used up to this point would be appropriate for this and so in this case i'm going to stick one more off of here and so the way this works this is now no longer again a simple substituent it's what we call a complex substituent and we have a systematic way for naming these as well and so up to this point we've circled the parent chain in blue and then we've got this lovely substituent here problem is we're also going to circle a longest chain for this guy as well now when you've got one of these complex substituents it's a substituent with its own branches a branch coming off the main chain that itself has branches what you want to do is identify the carbon that's attached to the main chain and he's going to get the designation number one and starting with him you want to start with him as number one and go through the substituent to get the longest continuous chain within the substituent and so with him number one i can either go left and get to two here or go over to the right and get two here and i can get a longer chain going off to the right and so i'll make him number two and then whether i go up or go to the right either one of those is going to be number three and so i'm gonna circle this guy as now the longest chain in the substituent now so a little tricky here and that's three carbons long and again being a substituent we'll name it with a yl suffix a while ending and the three carbons would be propyl and then the way it works is then you name the substituents that are coming off the substituents if you will and in this case they're both methyls so we have two methyls coming off the propyl and again the key is don't call this propane because it itself is a substituent or part of the substituent so we call it propyl and so we've got some form of dimethylpropyl substituent and so if we just want to name this substituent here we see that we've got methyls at carbons one and two and so this would be called a one comma two dimethyl propyl group cool and that's what the systematic way of naming a complex substituent here now when you name a complex substituent if you're going to put it into the actual name of the entire compound then you always need to put it in parentheses that's important and the idea is that a lot of these complex substituents start with numbers so and then if you give the chain locator of where it's attached to the main chain then you put another number at the beginning and then you just get this garble of numbers and it's like well which was which mean well if you put the complex substitute in parentheses then you know that the numbers inside the parentheses are part of the complex substituent and the number outside would be the chain locator of the parent chain instead and so if we name this entire compound here this is going to be six hyphen and then parentheses and our substituent is gonna be that one two dimethyl propyl so one comma two dash dye methylpropyl and then the parent chain here again is dotacane 12 carbons long cool and that's how the systematic way at least of naming complex substituents all right so i know what you're thinking you're like chad you said we don't have to name anything longer than 12 and you're right i just wanted to draw a really long parent chain so that everything coming off it's definitely going to be a substituent but we're definitely not going to name this as a parent chain or anything our focus is going to be on the substituents i have coming off this parent chain so first one i have coming off right here is this guy and my question for you is what would i name this as a substituent well in this case it's got one two three carbons and so it would just be a plain old propyl group and that is a simple substituent now if you look at having three carbons here and i'm going to kind of put them off here just three carbons so and if i want to attach these three carbons to a longer parent chain i've got two options i can attach it through either of the end carbons and that's what you get when you attach the propyl group here so notice i'm just attaching that last bond i'm just drawing it into one of the end carbons of propane but i have another option what if i attached it through that center carbon instead and that's what you get here instead and we couldn't call this a propyl group and again this is not a straight chain substituent it's branched and as a result it's a complex substituent now it turns out if for complex substituents if they have just three or four carbons you have an option there is turns out a common names for these smaller ones and you've got to know those common names or you could still use the systematic way we just talked about so but you gotta know both you're on the hook for both now again typically when you name it if you're naming it and the question on the test that you're taking is you have to name it usually either one is acceptable but the problem is you might be given a name and then have to draw a structure and so you've got to be able to look at the name and then know how to translate that into a structure as well so you do got to know both you're on the hook here so it turns out for three carbons these are only two options it's just a regular plain old propyl group or the only isomer of propyl that exists we call isopropyl all right that's three carbons now what if we add an additional carbon here in fact let's just start from scratch here and make it four carbons long let's start here one two three four there so now this is not a propyl group it's a butyl group but once again we have a couple of options here so there's four carbons and if i attach this to the main chain from either end that's how you'd get just a plain old butyl group okay so but my other options is i could attach it from the second one in from the left or the second one in from the right and it doesn't matter which one i choose it's the same thing either way but that's going to lead me to another option and so in this case there's my four carbons but instead of attaching it through one of the ends i'm going to choose one of these two middle carbons instead now if you look at these two middle carbons these two carbons are each and again before it's attached to the main chain here but they're attached to two carbons and if you recall we did a lesson classifying those and those are called secondary carbons so and notice once you attach it to the parent chain it actually turns into a tertiary carbon it'll be directly bonded to one two three carbons not just two but we're going to name this based on that root structure here before it's attached to the main chain and so it turns out it's still got four carbons we're still going to call it some form of butyl group but we'll call it a sec butyl group instead and it's hyphenated so sac butyl in this case so we have plain old butyl and now we see that we've got a sac butyl where it's attached through one of the secondary carbons and again it's named as a secondary carbon before it's actually attached once again i attach it it turns into a tertiary carbon but the name comes from what it looks like before it's attached so there's our sec-butyl but with four carbons it turns out we actually even have more options because with four carbons not only do you have a straight chain possible you also have a branched four carbon chain as possible as well and so we have all three of these carbons on the ends and they're all equivalent and so if you attach it through one of these carbons on the ends that's going to give you one structure let's see what that looks like down here as well so in this case there's that lovely structure and whether i attach it to this guy this guy or this guy it's all the same thing and we'll go there and so when you attach it to the full carbon branch structure through one of the outside carbons that's what we call iso butyl and notice the difference here sec-butyl is hyphenated whereas isopropyl and isobutyl are not hyphenated that'll be important in a little bit so but that's isobutyl and iso anything it turns out is going to be a straight chain that ends with what i like to say a fishtail so it looks like a you know drawing a fish tail to me or some people just say ends with a y so you could have isopentyl you can have isohexyl and this is a straight chain that at the very end forks into a y shape if you will cool so that's our isobutyl group but the other option would be attaching it to the middle carbon of that branched four carbon structure and if you notice we're going to be similar to the way we did the secondary one well this carbon right here is directly attached to three other carbons and is a tertiary carbon and so we're going to call this tert butyl short for tertiary butyl and so in this case so that middle carbon there is like this one and i've kind of changed the shape a little bit because that's how it would look when you actually drew it out and stuff so but that is your tert butyl group cool and so with three carbons we just had propyl and isopropyl but with four carbons there's butyl sec-butyl isobutyl and tert-butyl and tert and sec-bula are both hyphenated again i'm pointing that out it'll be important so when you go up to five carbons you actually have like eight different versions and we don't typically make students know those now again these are all these common names and they're totally acceptable now the reason i was pointing out the hyphenation here and stuff is how they're alphabetized so it turns out these ones that are hyphenated sec-butyl and tert-butyl are actually alphabetized not by s or t but by b for butyl and the truth is you're never going to have a sec-butyl and a tert-butyl in the same molecule and if you did i have no idea which one would actually win the tie from an alphabetical standpoint i've never seen it happen in 20 years so but these others there's no hyphens in them and it's just the first letter so for isobutyl or isopropyl that they're actually alphabetized by instead so definitely one thing to keep in mind there you should also again realize that you could totally see the systematic names for these as well so if we look at like the isopropyl so there'd be carbon number one the one attached to the main chain so again keep in mind there's our main chain so i'll circle it just like we've done so it looks familiar so there's our main chain and then this would just be a two carbon branch that has a another single carbon branch coming off the branch and so once again when you name it systematically the carbon directly attach the parent chain that's carbon number one and then get the longest continuous chain in the substituent you can get from there and so whether it went left or right it was going to be two carbons that's an ethyl group and in this case it has a methyl attached and so if you look at your handout right next to isopropyl it's called a one methyl ethyl so if we do the same thing for the sec-butyl group over here again this is going to be carbon number one and starting with him as number one i can number through two three my longest continuous chain from there is going to be three carbons long and then i'll have a single branch coming off that branch which again is a methyl and so this would be a one methylpropyl group take a look at the isobutyl group and again carbon directly attached to the parent chain is number one and numbering from there number two and then either one of these could be three and so it's a three carbon branch with another one carbon coming off it another methyl and this with an isobutyl group could also be called a two methylpropyl group and then finally for that tert-butyl group again the carbon directly attached to the parent chain is number one and then any one of these could be number two so i'll just choose him and this one i'm going to write out real quick so this is going to be called a 1 1 dimethyl ethyl group let's write that out so you can see that on your study guide there as well so one one dimethyl ethyl and again if you're going to actually name it as part of a compound complex substituents when you name them systematically always go in parentheses if you use any of these common names they don't go in parentheses but when you name it systematically that is when it goes in parentheses and there's one other special case here you need to know that when you're naming them systematically like this because you know you get numbers in there and things are complicated whatever the first letter in parentheses is that's what it's going to be alphabetized by even if it's part of a numerical prefix so normally for regular simple substituents we don't use the die the try the tetra as part of the alphabetical at all but for a complex substituent whatever the first letter in the entire name that shows up in parentheses is that's what it's going to be alphabetized by even if it's part of a number prefix so in this case this will actually be alphabetized by the letter d in dimethyl ethyl cool so now we've seen how to name our complex decisions both in a simple way and the systematic way and again if you've got complex divisions that have more than four carbons in them you're just going to only have the systematic way available to you at that point so you definitely got to know both like i said again so now we've got a couple of complicated examples here that are both going to involve some complex substituents and we're going to name them so first thing you're going to do same thing we've always done is find the longest continuous carbon chain so i can see here that's from this branch point whether i go off to the left or down below it doesn't matter either way so and at this branch point i can definitely see when i go left and when i go right i can get one two three four five or one two three four five whereas here i'm only gonna get one two three so the longest continuous chain does not include this guy that's gonna be part of a substituent but it'll definitely include and in this case again either down or across it doesn't matter and so then the rest are left to be substituents so there we have an ethyl group and there we have another ethyl group but here we got a problem and in this case it's got one two three four five total carbons you don't have any common names for something like this so to name it then you're gonna have to number the longest chain starting with number one as the carbon directly attached to the parent chain so there's one there's two and either one of these could be three and so this is going to be some form of propyl group with a couple of methyls attached and so in this case i can see that it's a one two dimethylpropyl and that'll go in parentheses and so in this case we're going to say diethyl is part of the name but the dye won't be part of the alphabet because these are just simple substituents so it's going to be alphabetized under the letter e but my complex substituent is going to be alphabetized whatever the first letter is and d comes before e so we're going to say the dimethylpropyl first and in this case if we number that longest continuous chain i can go one two three or one two three and that's a tie okay one two three four five six to the second substituent one two three four five six to the second switch still a tie so one two three four five six seven eight nine for the third substituent and then one two three four five six seven eight nine for the third substituent and in this case it's an absolute tie so and it and it turns out it's even more than that it's just an absolute tie this molecule is perfectly symmetrical and so whether i have the ethyls at three and nine well the other way they'd be at three and nine and this complex which is six and no matter which way we number it it's exactly the same thing and so it doesn't matter so i'm just going to go left to right because that's what i normally do so 1 2 3 4 5 6 7 8 9 10 11. so and in this example you know if you're from certain parts of the world you're probably more likely to go right to left and for a symmetrical molecule it doesn't matter all right so we'll name the complex one first again it comes first in the alphabet and we see that its chain locator is six and so we're gonna say six hyphen parentheses one two dimethyl dimethylpropyl and the parentheses and then three nine diethyl and then our longest chain is 11 carbons and recall that that is undecane one big long word all right so one more example here and yet again our longest continuous carbon chain will definitely from this point one two three four one two three four one two three so it will definitely include these branches off here and again i could have circled this carbon instead of this one and i could have circled this one instead of this one it was arbitrary they're totally equivalent so but i had to make sure that this is my long skinny chain it does not involve that that's just going to be a substituent along with these methyl groups so now this substituent right here is again a a substituent that itself has branches coming off it's a complex one but it only has one two three four carbons because it has four carbons you could name it as a uh the common name for that complex division or you could use this systematic way and both are totally acceptable according to iupac rules and so you really got a little bit of flexibility here so i've got a couple of methyl groups here but this guy could be an isobutyl notice it ends with the y so that's an isobutyl or that could be carbon number one and then two and then either one of these could be three so your longest continuous chain is three carbons that's a propyl group and there is a methyl coming off that propyl so that is a two methylpropyl so let's write both those out there so this could be a two methylpropyl in parentheses alphabetized under the letter m or it could just be an iso butyl alphabetized by the letter i all right in this case numbering this thing so one two for substitutions at two if we go left to right one two so one two three four five for the second section one two three four five for the second one two three four five six seven eight for the third one two three four five six seven eight for the third once again i've given you a perfectly symmetrical molecule it wouldn't make a difference which way you numbered it so this time i'm gonna go right to left just for the fun of it doesn't matter either way it's gonna get the exact same name regardless for this symmetrical molecule uh did i count that right that i missed one one two three four five six seven eight nine great all right so we can see that we've got methyls at two and eight so oh this should be fun so we've got methyls at two and eight so we got something tricky here so if you notice methyl and methylpropyl they both begin with methyl which one would come first in the dictionary well methyl would come before methylpropyl because you'd keep adding more letters here and so if you call this thing a 2-methylpropyl you'll name the 2-methylpropyl second when you list the substituents but if i call it an isobutyl group i comes before m and i'll name the isobutyl group first so it actually matters which way you you name this thing so because the order in which you name the substituents is going to change now again both names are acceptable so and you've got to be prepared for both so let's take a look at this here real quick so in this case let's start with the systematic name and in that case again methyl's going to come first so we're going to say 2 comma eight dimethyl and then five two methylpropyl in parentheses so and i'm running out of room so we'll just keep continuing this on and nine carbons would be non-egg one big word one big word whereas had we named our complex substituent with a common name isobutyl then we would have named the methyl's second and the isobutyl first so this would have been five isobutyl and then two eight dimethyl and once again parent chain would be not in cool so just a lovely tricky example where again the order in which the substitutions might change depending on if you use the common name or the systematic name for that complex substituent now if you found this lesson helpful please consider giving me a like and a share pretty much the best thing you can do to support the channel and if you're looking for the study guides that go with these lessons or if you're looking for practice problems on naming 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