naming bicyclic compounds that'll be the topic in this lesson we'll have three different variants we'll have bridged bicyclics fused by cyclics and sphero bicyclics so that we'll talk about in this lesson in my organic chemistry playlist now in this chapter we've already covered a lesson on naming alkanes and then we moved on to naming complex substituents and this will be the last thing we need to learn how to name so before we proceed on to talking about various conformational structures we need to look at and recognizing for alkanes now if this is your first time joining me my name is chad and welcome to chad's prep where my goal is simply to make science both understandable and even enjoyable now this is part of my 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 special set of rules for naming these bicyclic compounds and it turns out there's one set of rules that will work for both the bridged and fused by cyclics and then we'll have a similar set of rules but a little bit different for our spiro bicyclic compounds as well all right so how do you recognize the difference between these and stuff like this so one thing you should know about our bridge bicyclics is there's a couple different funky ways we often draw them now we can draw them in this kind of a sideways perspective that's a little bit new and this will be do so or we could kind of draw it in the similar fashion what you've seen now what you see here is you've got a seven-membered ring that's a cycloheptane by the old standards but in this case we can't just simply call it a cycloheptane because we also have another ring right here like if you look right around here that's a ring now these bonds right here we call these wedged bonds and they're meant to give us three-dimensional perspective and for a wedge bond it means it's coming out of the board like this is like a handle out here so that's what those actually mean and so we've got this lovely seven membered ring right here but if we look here there's a five membered ring right here and if we count around through here that's another ring as well and so we've got multiple rings on this we call these bicyclics for reason and there's a whole special set of rules we named these so you don't like find the biggest ring you can find in it name it the parent doesn't work that way just a whole new set of rules so first thing you want to do is in all your ring structures you want to just count up the carbon so in this case we got one two three four five six seven and there's an eighth and so as a result this parent compound of this name is going to be called bicyclooctane is going to be the name so let's write that out so let's get by cyclo and then octane but notice i saved a little room in the middle and we'll see why that is here in a sec next thing to figure out so it turns out there's going to be three numbers placed in brackets in the middle of this and i definitely didn't leave enough room here let's make that just a little bit bigger with our brackets so and we're going to put three numbers in there separated by periods and those numbers are going to come from the structure here so we have to identify what are called bridge head carbons here and that's where it gets this name these bridge bicyclic so they've got these bridgehead carbon atoms and the bridgehead carbon atoms are the carbons in this case this one here and here or here and here that are part of any of the rings so whether you look at it as this ring right here or this ring right here or this ring right here it's only these two carbons that are part of every single one of those rings so they're called the bridgehead carbons and what you want to do is identify how many carbons are in between each of those bridge heads no matter which pathway you take so if we look like going around say the left hand side i've got a carbon there and a carbon there and so to get from bridgehead to bridgehead there's two carbons in between if i go around the other side there's a carbon there and a carbon there and a carbon there and so there's three carbons in between those bridgeheads as you take this pathway to get from bridgehead to bridgehead and then here this right here represents a carbon as well and so in this pathway there's just a single carbon as you go from bridgehead to bridgehead and so those are the three numbers we're going to use actually the number of carbons in between we don't count the bridgeheads themselves but just the number of carbons in between and you put them in descending numerical order from highest to lowest and so in this case this is bicyclo321 octane that's how this works cool so that's a simple bridge bicyclic but what happens when you get substituents so in this case once again we'll recognize those bridge heads so but we've got a substituent sitting out here and that's just simply a methyl group and so substituents you're going to name them the same way we did with regular alkanes you're just going to put them at the beginning of the name before the parent but you've got to give the appropriate chain locator which means we have to learn how to number these as well well the way this works you're always going to give one of the bridge heads atom number one that's the way it works so let's just say i choose this one right here he's number one and then the way it works because we name this from highest to lowest on those number of carbons in between the bridgeheads you number through the longest chain of carbons from bridgehead to bridgehead first so here that was this three pattern so again we had three over here two over here one up here and so if i named him number one then i want to go through here to two to three to four and the other bridge head would be at five and then you number three to the second longest ring which is this one so then six and seven and then any other carbons to the third ring you need to give that's going to be eight and now we've given all eight carbons and bicycle three two one octane a number and in this case that methyl is attached to carbon number seven now i just arbitrarily chose this bridgehead to be number one i could just as easily have chosen this one to be number one and had i done that then this would be one and again i would number through the longest chain first so two three four five six seven eight and i see actually that gets me a better method just like we've done in the past if i have a method of numbering so there are two different equivalent methods of numbering but one gets me the first substitution when i come across a lower number that's a superior method and so numbering this in red is actually the proper way where i get my methyl group located at position six rather than position seven and so we'll get rid of these other numbers and so when i chose this top carbon to be the the number one at the beginning i had a 50 50 guess i guessed wrong and so in this case i should have chose the bottom carbon to be the bottom bridgehead carbon to be number one because i can get my first substituent my only substituent a lower number and so in this case this is now going to be 6-methyl not 7-methyl and then bicyclo 3 period 2 period 1 octane one big word no spaces in here anything like that alright so that's a bridge by cyclic and we learned how to number it just in case you have a substituent and once again just a reminder many of you may not even name any bicyclic compounds so some professors and textbooks choose to leave these out but many of you are going to be on the hook for these so we're definitely covering them now moving on to fused bicyclics and you're fused by cyclics you can find your bridgehead carbons yet again and what makes it a fuse bicyclic is that your two bridgehead carbons are actually bonded together directly so in in the bridge bicyclic case they're always separated by at least one carbon or more no matter which path you take but in the fuse bicyclic in one of the pathways they're directly bonded to each other all right but it actually follows the same pattern so in this case the number of carbons as you go from bridge head to bridge head if i take this pathway on the left there's four carbons in between if i take the pathway on the right there's two carbons in between and if i take the direct pathway there's zero carbons in between them and that actually gets included in the name here in this case so with a fuse your third number is always going to be a zero and that's definitely got to be included in the name and so in this case we've got six seven eight total carbons again so this is going to be some form of bicyclooctane yet again and four two zero octane so still numbering them in highest to lowest descending order and in a fused bicyclic that third number is always going to be a zero but same set of rules now the sphero bicyclics are going to be a little bit different and your speedo bicyclics typically have just two rings that share a single common carbon and we call that the spherocarbon now in numbering these and things of a sort it works a little bit different so we're going to have to use a slightly different set of rules so first thing i want to do is identify that spherocarbon so i'll do that here in this case so and same kind of thing here you want to count the number of carbons as in this case instead of going from bridgehead to bridgehead it's just taking each pathway to go from the spherocarbon back to the spherocarbon how many carbons do you pass so here one two three four and here one two three four five and those are your numbers but instead of going from highest to lowest with a sphero compound you're going to go from lowest to highest and instead of starting the name off with by cyclo the prefix for a sphero compound is just sphero and so in this case we're going to call this sphero so and then lower number first higher number second so sphero 4.5 so and then total number of carbons and notice your total number of carbons is always going to be your two numbers plus the sphero so total of 10 so this is going to be sphero45 decane all right so one last example what do we do when we've got so a substituent well then you have to learn how to number these things as well and that's unfortunate so there's our and you don't make your spirocarbon number one that's tricky so whereas back over here we made one of the bridgehead carbons number one in this case it's not going to be the spherocarbon getting the designation number one so again we've got three i'm sorry four carbons in between uh from spirit of spiro back to itself over here and five over here and in this case it's that methyl group we need to know where he's located on that parent spiro chain here in this case well it turns out first thing you want to do is realize that we give the lower number for the higher number and so you're always going to number the lower chain before the higher in this case recall back with the bridge bicyclic and the fused bicyclic we always numbered through to the and i should look at it back here we numbered through the bigger one before we did the smaller one so like here we went through the started with the bridge set number one and we numbered through the longest chain first you number the longest then the second longest and then the last is where you get the numbers but with the spiro it's backwards since we number these backwards you number three the smallest first and the way it works is here's our smaller side and one of the carbons next to the sphero is number one and choose one so so i'm gonna make him number one i could have made it either one in this case and then you number three now you couldn't make it either way if one of the ways gives you a lower number for your substituent then you should choose that way same kind of thing we've gone before so but if i make him number one he's two he's three he's four and the spiro is five and then you go through numbering go right through the spiro and either go down to here or up to here make one of these two number six whichever one will get you your specific lower number now notice whether i started with this guy's number one or this one down here is number one it wouldn't have made a difference because my substituent's actually on the other ring and so in this case though the question is which one of these gets to be number six well it's definitely gonna be this top one that way i can get my methyl group located at position seven had we made this guy down here six have been six seven eight and it would have been nine methyl seven methyl is definitely superior and now we found our way of naming this so we'll start off with 7-methyl so and then spiro 4 5. decade cool and that's all there is to naming bicyclic compounds so and again not all students are going to get this as part of their curriculum in undergraduate it's just the way it works so some books include it some don't some professors include it some don't so but a really good chunk do and so it's definitely worth my time to go through so and even past that a lot of students will get bridged and fused and student a lot of professors just leave out the numbering system altogether and never ask a question involving one with substituents that's possible too and yet again then a lot of professors will even just include the bridge and the fuse but leave out the spiro and if they do include spiro they're probably not going to include one with substituents or you know things of a sort so this is of lesser importance than all the other nomenclature we've done but again for some of you students you will need all of this for others who knows so the rest of this chapter is going to be dealing with the confirmations of alkanes and before we move past nomenclature because this is something we're going to keep revisiting over and over again throughout the course but before we move past it for this chapter i just want to address one thing you'll need for the future it's not really too relevant now but i did want to file it away in your study guide so you'd have a copy of it for reference later so as we encounter different function groups throughout organic chemistry throughout the entire year we're going to learn a new uh twist on nomenclature something new we have to add for naming that functional group and we'll find that for most of those functional groups they're going to have a different suffix at the end of the parent chain so whereas others will be named as a substituent and for some of them you might have the option to name it as part of the parent chain or to name it as a substituent depending on its priority so if you look at that list you've got a whole host of priorities with carboxylic acid at the top and then acid anhydride and so on and so forth and usually you're going to get one functional group with the highest priority that's going to be named as part of the parent chain and then if you have any additional functional groups in your molecule past that one then they're going to be named with a prefix instead so as a substituent and so you kind of got to know this general ranking that way you know who who's going to be named as a suffix on the parent chain versus who's going to be named as a substituent with a prefix instead so that's kind of the idea behind that list and like i said we haven't learned how to name any of these functional groups yet they're going to come you know a couple here a couple there throughout the rest of the year um so but i did want you to have this as a reference so that you know for the future i will allude back to this time and time again throughout the course 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 practice problems or the study guides that go with this check out my premium course on chadsprep.com