Naming Alkyl Halides IUPAC Nomenclature

in this lesson we're going to talk about how to name alkyl halides so let's start with this example how can we name this particular alkyl halide feel free to try if you want to well the first thing we need to do is count the longest chain now we need to count it in such way that the substituents will have lower number if we count it from left to right the bromine atom will be on carbon too if we count it in the other direction the bromine atom will be on carbon four and so we don't want that therefore this is going to be called to bromo because the bromine atom is on carbon two and there are five carbon atoms in the longest chain so that corresponds to pentane so it's to bromo pentane now let's try this example go ahead and name the following alkyl halide so we need to count it from left to right and so we have six carbon chain which corresponds to hexane we have chlorine at carbon two and three so this is going to be two comma three dichloro hexane we need to use the prefix die because we have two chlorine atoms and we need to use comma to separate the numbers and the - to separate number from letter so here's another one that you could try so in this case which way should we count from left to right or right to left let's do it both ways and let's see which way makes sense so let's go from left to right firs so this will be 1 2 3 4 5 and we need to write the substituents in alphabetical order so bromo comes before coral so this case is going to be 2 bromo - 4 coral and then pentane because there are 5 carbons now if we count it in the other direction it's going to be 4 bromo - 2 - chloro pentane so which way is correct way to name this so in both cases is listed in alphabetical order in such situation you want the first group to have the lower number so you want to put the numbers in ascending order after you alphabetize the substituents so this here is the best answer so this was the right way to number it let's work on another example how can we name this particular compound so we have an alkene and an alkyl halide so which group should we give more priority to the alkene or the alkyl halide we need to make sure that the alkene has the lower numbers so we need to count from left to right as opposed to right to left so we have fluorine atom on carbon five and the alkene is between one and two and there's six carbons so instead of saying hexane it's going to be hexene and the double bond is that carbon one we have to pick the lower number of those two numbers so to put it all together it's gonna be five Florin - one - hexane and so that's how we can name this particular compound now what about this one let's say if we have an iodine atom on cyclohexane ring how can we name it now we don't have to worry about number in it because it's automatically going to be on carbon 1 and so we don't have to say one iota cyclohexane this is simply Yodle cyclohexane try this problem so now that we have two substituents on this cyclopentane ring since there's total of five carbons we do need to number the substituents so which one shall we make number one bromine or methyl well comes before so we're gonna have to offer ties in and so we want this one to have the lower number so I'm gonna make this number one now which direction should we count clockwise or counter clockwise if we go counter clockwise the methyl group will be on carbon four if we go let's say clockwise it will be on carbon three and so we want the substituents to have the lowest numbers possible therefore to put it together it's going to be one bromo and then three methyl and we have total of five carbon atoms in this ring so it's going to be cyclo pentene now here's the next example this time we're gonna have three substituents as opposed to two or one take minute and work on this example so we have bromine or chlorine and methyl so how should we put it all together shall we make the bromine atom carbon one even though becomes before CNM let's see what's gonna happen that means the chlorine atom will be on carbon three and the methyl will be on carbon four and so we're gonna get the numbers 1 3 4 now if we make the chlorine atom number one we're gonna have to go in this direction and so the methyl will be on two bromine will be on five so that will be one two five and if we go in this direction it's gonna be very bad because the methyl will be on six so we're not gonna consider that but let's say if we put the run on methyl and we count in direction that's closer to the other substituents this will be 1 2 & 4 so 1 2 & 4 is less than 1 3 & 4 because 2 is less than 3 it's also less than 1 2 5 because 4 is less than 5 so this is the best way to count it because it gives us the lowest number for all the substituents so we have 4 bromo al chlorine on 2 so that's 2 chloro and the methyl on 1 and there are 6 carbons in this ring so that's cyclohexane ring so let's put it all together so we need to put it in alphabetical order so it's going to be 4 bromo and then 2 plural and then one methyl cyclohexane and that's the answer consider this molecule ch3 Br what is the common name and the systematic name for that molecule the common name for ch3 BR is methyl bromide because we have methyl group attached to the bromine atom the systematic name this is going to be methane but it's simply just going to be bromo methane and that should be one word so let's look at another example try this one so the common name is going to be ethyl chloride and the systematic name is simply chloro ethane we don't have to say one chloro ethane because if you put the chlorine atom on this carbon or in this carbon it's still going to be carbon one now what about this example try that what is the common name for that molecule the fluorine is attached to an isopropyl group so this is going to be called isopropyl fluoride or the IU pack name it's too floral because if you count it the fluorine atom is on carbon 2 so it's too floral propane let's consider two last examples try those two so starting with common name this is called propyl iodide and for the IU pack name we could see that the iodine atom is on carbon one so we could say it's one iota propane now for the example below it the chlorine atom is attached to tert-butyl group so the common name is going to be tert-butyl chloride now for the systematic name I'm going to draw it like this so it's easier to see it so this is going to be carbon one two and three so on carbon two we have chloro group and methyl group so this is gonna become it's gonna be called 2-chloro - 2 methyl because we need to put it in alphabetical order and then propane since we have three carbon pantry and so now you know how to name the alkyl halides using common names and u-pack nomenclature