in this video we are going to focus on classifying compounds as being either stereo isomers anomers diomer miso compounds and even constitutional isomers but you need to understand that anater and ders are a subcategory of stero isomers so we need to distinguish constitutional isomers from stereo isomers first so let me give you two pairs of cont so let's compare the first two what is the relationship between these two and what is the relationship between these two molecules well the first two are known as stereo isomers the last two are constitutional isomers so what is the difference between a constitutional isomer and a stereo isomer first for all isomers they all have the same chemical formula but a different structure now constitutional isomers differ in their connectivity the alcohol in the first molecule is attached to Carbon 2 and the second molecule is attached to carbon 3 so constitutional isomers are connected differently stereo isomers are connected the same way notice that in both cases the bromine atom is attached to the same carbon that is carbon number two but notice that the arrangement in space is different even though both bromine atoms are attached in the same carbon the first bromine atom is directed out of the page it's towards the front the second one is behind the page towards the back so even though they're connected the same their spatial Arrangement is different which makes them stereo isomers now this particular stereo isomer is known as an ananur ananur are basically nons super POS posable mirror images of each other notice that the Kyo Center is different in this molecule compared to this one the caryo center has been reversed whenever you change the caryo center you're going to have an enan if all CH centers change consider these two molecules describe the relationship between them let's use chlorine this time so what is the relationship between these two molecules notice that the first chyo center Remains the Same the second chyo Center changes when some of the chyo centers change their configuration but not all of them what you have is a dma so for example let's say if we have the let's say if there's three chyo centers r r r and we're comparing it to another molecule that is rsr this would be a dmer but now let's say if we have rrr and another moleculees SSS and if there's no plane of symmetry then we would have aners so to get an anater all of the car centers must change but to have a dmer only some should change but not all now what is the relationship between these two molecules notice that all Caro centers have changed their configuration the first one change it was in the front now it's in the back and the same is true for the second one so does that mean that we have a pair of anatas which is the type of stereoisomer notice that we have a plane of symmetry so therefore these molecules are ayro molecules an ayro molecule can never be an anater instead what we have is a pair of miso compounds miso compounds have a plane of symmetry and even though the chyos centers are reversed these compounds are actually the same they are identical molecules let's try another example now what about these two how would you classify them so notice that the first chyo center changed the O group was in the front now it's in the back and the second Kyro Center changed as well so all Kyro centers were revers in their configuration and notice that we do not have a plane of symmetry the o H group on the left side of the line is in the front and the other one's in the back so there's a lack of symmetry therefore these two are known as aners they are mirror images of each other so whenever all Cho centers change and if there's a lack of symmetry you are going to have a pair of aners if all Carro centers change and if there's a plane of symmetry that's a good indication that you have a miso compound and if some Carin is changed but not all then you have ders and if they're connected differently then you have a case of constitutional isomers how would you describe the relationship between these two molecules so feel free to pause the video and take a minute to answer this question so notice that the first Kyo Center remained the same but the second one changed whenever only some carers change but not all then we have a case of ders by the way you can also describe it as CIS trans geometric isomers this is the CIS iser this is the trans isomer CIS trans geometric isomers are always ders but not all diers are CIS trans isomers so these two would be CIS trans geometric isers on the left we have the trans iser this is Trans tutin on the right CIS tutin now what about these two are they identical or are they different what would you say these two molecules are identical this carbon is not chyal the left side is identical to the right side so because the carbon is not chyro there's no need to use the symbol to put it in the front or in the back so these are identical molecules what about these two what is the relationship between these two molecules these are not dimers even though some chyo is change but not all notice that the connectivity is different here the two bromine atoms are on carbons 1 and three and in the molecule on the right right side the two bromine atoms are on carbons one and two so we have a case of constitutional isomer since they're connected differently let's try another example describe the relationship between these two molecules so what's your answer so notice that we have a plane of symmetry in both molecules and a car Centers do indeed change so it can't be an aners due to the line of symmetry so therefore these two are miso compounds they are identical to each other