foreign welcome to my channel on chemistry lessons this is a B Tech applied science it's unit 5 chemistry and we're going to be looking at isomers so this is under the learning A2 and it's right up at the very beginning part of the introduction now if you haven't seen previous videos that look at the different types of formulas such as displayed structural and skeletal but I do suggest you start there first and you will find some links in the description below so by the end of this video then you are going to be able to recall and identify different types of isomerism if you don't already subscribe come and ask that you do your support it's very much appreciated and please use the likes and comment features so I summarize them then there's actually two subgroups to isomerism the structural isomerism and stereo isomerism and then there are other subgroups so there's three types of structural chain position and functional group and there are two types of stereoisomerism geometric and Optical and what we're going to do is we're going to go through each one in turn we're going to Define them and then we're going to look at some examples first off then definition for an isoer an isomer is compounds that have the same molecular formula in other words the same number and type of atoms however they are arranged differently and that gives the molecules different properties let's move across a structural isomerism then so structuralized isomerism means they have the same molecular formula but a different structural formula again if you haven't seen previous video on structural formula I suggest you do look at that the three subgroups of structural formula then we have chain isomerism now chain isomerism is when the molecules only differ by their arrangement of the carbon atoms in the base chin and the two main examples here would be straight chain and branched so if I pick a molecule if I go for C 5 h 12. now you might assume that that's just pent in and pentane would be one of the isomers so it could have a five carbon straight chain let's this would be a straight chain isomer C5 h12 then this would be a displayed formula that I'm drawing here it is much quicker and easier to use skeletal so I will do from now on I'm going to use skeletal from now on if you're not comfortable with skeletal then we need to look at previous videos so that we are so that's the skeletal of pentane and that's the displayed for pentane the other isomer or a branched isomer would be two methyl butane or I could also have dimethyl propane so these would be known as chain isomers a position isomer this is when the molecule differs by the position of the functional group so we won't have functional group isomers of alkanes because alkanes are a very simple basic functional group where it's just carbons and hydrogens we can though have position isomers of alkenes for example that's Bute one in if I move that functional group to the middle that's now Butte to in so that's a functional sorry that's a position isma I could also have a position isomer of a Halo arcade that's two bromo butane or I could have one promo Beauty they too would be classed as position isomers of bromorbutane functional group isomers and then we have the same molecular formula this time and but the functional group is different and these are quite rare and we're going to look at two examples as cyclic alkanes and alkanes and aldehydes and ketones first example then a cyclic alkane if I draw cyclohexane that is in fact c6h12 or if I draw hexane they are both c6h12 however the one on the left is classed as a cyclic alkane and has similar chemical properties to alkanes the one on the right is an alkene and it has similar properties or properties of alkenes less common then and not necessarily covered too much in your btec spec would be aldehydes and ketones if I look at propan Al propane Al looks like this propane on looks like this so this is propan Al and propan own this is an aldehyde on the left and this is a key tone on the right that's actually a different functional group but as I've said you don't cover those in much detail in this unit it's mostly your alkanes and your alkenes that you need to be concerned with so back to the beginning then so we've covered the three types of structural isomer we now need to look at the stereoisomerism definition for a stereoisomer they have the same structural formula but different 3D arrangement in space so notice how that's definitely a different definition to your structural isomer your structural isma had different structural formula and same molecular formula this time for a stereoisomer they do have the same molecular formula they do have the same structural formula but it's a different arrangement in 3D space two types of steroid right summers in them we've got geometric isomerism sometimes called EZ and this occurs in our alkenes due to the restricted rotation around the double bond that means that double bond locks the groups in place and they can't there's no free rotation that Bond can't rotate let's have a look at some examples then so I'm going to draw like carbon carbon double bond here and I'll draw a carbon carbon door on the right we've got a ch3 and I'm going to put a h and then on this side I'll put a h and again I'll put a ch3 so in order to have stereoisomberism each carbon in the double bond must have two different groups on each carbon so this has a ch3 and this is a hitch these two groups are definitely different and again on the right hand side we must have two different groups which we do we have ch3 and H they are different groups so what I can do is if I change the position of those groups or just one of them let me see we've now got a different arrangement in space so in this case the ch3 groups are on opposite sides of the double bond and on the left hand side they'll see it three groups on the same side now I have done a video on or detailing the EZ isomerism so again I suggest you watch that first because this is just a real quick overview of geometric isomerism I do go into detail and we do use the rules of assigning priority so I do suggest you watch that video at some point and you'll see in detail how we identify and name those geometric isomers okay the final type of stereoisomer is the optical isomers and this is identified or defined as non-superimposable mirror images of each other and they most commonly occur when a carbon atom has four different groups attached and we call this a chiral carbon or an asymmetric carbon now I don't believe this is covered in which detail at all in this spec but I will cover it this is more of an a level thing so I'm gonna have four different groups attached to a carbon and I'm just going to make them up I'll say I'll have a ch3 we'll have a h we'll have an o h and maybe we'll put a chlorine there so that's four different groups attached to this carbon this carbon is identified as a carbon carbon so what I do is I draw it 3D and we know using the dash and the wedge that the 3D structure I draw two usual all straight line so sure they're in plain with the pitch I then draw a wedge to show coming out the page and I show a dash going into the page now I've randomly assigned these four groups I didn't have to put them in a specific place I can just put them anywhere randomly now the difficult part comes to draw the mirror image so I need to draw a reflection of this molecule notice how on the left the straight lines are the ones in plane are going straight up I have to draw a reflection now the wedge is here the solid wedge that shows it's coming out of the page my Dash is going in the page and I just draw the reflection of that molecule they are now non-superimposable mirror images and classed as Optical isomers I don't think you will need that level of detail I've not seen that asked in any past exam questions I would focus on the EZ isomers of alkenes so there's your big overview then there's your overview of your different types of isomers so I do suggest you do follow that geometric in a little bit more detail in my other video and I wouldn't worry or concern yourself with Optical isomerism other than being aware it exists with a definition I wouldn't worry about having to draw your different ones out on b-tech second year air level yes b-technor hopefully you found that video useful then and thanks for watching