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now that we know how to assign oxidation states to carbon let's look at some organic redox reactions and remember these definitions from general chemistry oxidation involves an increase in the oxidation state and reduction involves a decrease or a reduction in the oxidation state you might also remember that loss of electrons is oxidation and gain of electrons is reduction so Leo the Lion goes ger is a good way to remember that let's look at this starting compound here in this reaction and let's figure out whether the starting compound has been oxidized reduced or neither if you look at these three carbons on the left and these three carbons on the right there's no change to those carbons so there should be no change in the oxidation states of those carbons but when you look at this carbon right here the one I just marked in yellow right on the Left it's bonded to let me go ahead and draw that out it's double bonded to an oxygen and on the right it's bonded to a hydrogen and on the left it's bonded to a carbon but on the right here that same carbon right is now bonded to an oxygen on the right so it's still double bonded to an oxygen and has a bond to a carbon on the left but on the right now it has a bond to an OHA so that carbon has likely changed its oxidation state and we can go ahead and find the oxidation state using what we learned in the last video so remember you need to put in your bonding electrons so let's put in our bonding electrons here each bond consists of two electrons alright so we know that when we're doing oxidation states we need to think about electronegativity differences and carbon is more electronegative than hydrogen so we assign both of those electrons to carbon oxygen is more electronegative than carbon so oxygen takes all four of those electrons and we get to carbon versus carbon we can assume that those carbons have the same electronegativity and therefore for two electrons we're going to split those two electrons up we're going to give one electron to one carb and the other electron to the other carbon so this carbon is surrounded by three electrons and we know carbon should have we know carbon is supposed to have a number of 4 valence electrons around it so carbon supposed to have four in our dot structure here carbon only has three let me highlight them 1 2 & 3 so 4 minus 3 gives us plus 1 which is the oxidation state for this carbon so this carbon right here has an oxidation state of +1 on the left what about on the right let's go ahead and put in our bonding electrons all right so we know that each each bond consists of two electrons only put those in here and again we think about electronegativity this time on the right this carbon is bonded to an oxygen now so carbon loses those two electrons to oxygen my oxygens more electronegative oxygen takes this top oxygen takes those four electrons and again we split these two electrons so this time carbon is only surrounded by one so to find carbons oxidation state we know that carbons supposed to have four valence electrons and from that we subtract the number of valence electrons around carbon once we've accounted for electronegativity and that's only one electron now so four minus one gives us an oxidation state of plus three so on the right this same carbon now has an oxidation state of plus three so what happened in this reaction carbon went from an oxidation state of plus 1 to an oxidation state of plus three an increase in the oxidation state is oxidation so our starting compound was oxidized here so our stott our starting compound was oxidized in order for this to be oxidized we would need some sort of oxidizing agent so I'll write that down here really quickly we would need an oxidizing agent to accomplish this reaction and it's the oxidizing agent that itself is being reduced because remember whenever something is oxidized something else has to be reduced let's think about the other definitions for the other definition I should say for oxidation we know that oxidation involves the loss of electrons so let's look at that here on the left right carbon had three electrons around it and when we added a bond to oxygen right carbon lost these two electrons over here it had those two electrons on the left it had those two electrons on the right it lost those two electrons so now it's only surrounded by one and we see an increase in the oxidation state so it's like carbon lost electrons also there's a shortcut that you can use for this reaction let's let's think about what that shortcut would be let me use I'll use red still on the left this carbon with an oxidation state of plus one has two bonds to oxygen let me go ahead and highlight them here so here's one bond and here's the other bond on the right that same carbon now has three bonds to oxygen so here's one bond here's two bonds and then this bond over here so we've increased in the number of bonds to oxygen and that can tell us we have an oxidation really quickly without going through and doing all these oxidation states notice we lost a bond to hydrogen right so over here we lost this bond to hydrogen and we we we replaced it with a bond to oxygen so an increase in the number of bonds to oxygen or a decrease in number of bonds to hydrogen can tell you that your carbon is oxidized to let's do another one so our goal is to figure out whether this starting compound has been oxidized reduced or neither so again these three carbons on the Left right are the same as these three carbons on the right and there's no change in those carbons so therefore we would expect no change in the oxidation state same with this carbon so we're going to focus in on this carbon so on the left that carbon has a double bond to oxygen so we draw that in there and then it's bonded to a carbon on the left and a carbon on the right in our product that same carbon is now bonded to only one oxygen let me let me go ahead and do the only one bond I should say two oxygen and it's still bonded to a carbon on the left and still bond to a carbon on the right and it must have a bond to hydrogen in here it's not drawn in but it's assumed that you know that so let's put in that bond to hydrogen let's find our oxidation states so we start on the left and we draw in our bonding electrons and next we think about electronegativity differences so we know that oxygens more electronegative than carbon so oxygen takes those 4 electrons over here right we assume that the electronegativity is where these carbons are the same and so we split up those two electrons we give one electron to one carbon and one electron to the other carbon and same over here so the oxidation state for carbon would be four valence electrons minus this in this case we have two around carbon so here's two four minus two gives us an oxidation state of plus two so on the left this carbon has an oxidation state of plus two what about on the right let's put in our bonding electrons and again once we've done that we think about electronegativity and we can assign an oxidation state to that carbon so we know that oxygens more electronegative so oxygen takes those two electrons right again there's we assume that these carbons have the same electronegativity so we split up those electrons we split up these electrons but now carbon is bonded to you hydrogen so carbon is a little bit more electronegative than hydrogen so we just give both of those electrons to carbon and now let's find our oxidation state we know carbon is supposed to have four valence electrons around it and in our drawing here once we've accounted for electronegativity carbon is surrounded by one two three and four so four minus four is equal to zero and so this carbon this carbon now has an oxidation state of zero so that carbon went from an oxidation state of plus two to an oxidation state of zero that's a decrease in the oxidation state so carbon was reduced so in this reaction our starting compound was reduced alright so this was our starting compound was reduced which means we would need some sort of reducing agent to accomplish this reaction and it's the reducing agent that would be oxidized because if something is reduced something else has to be oxidized we could also think about our other our other definition for reduction gain of electrons is reduction and that let's look at what happened here so the electrons that were gained right were these two electrons right here because on the left we had this carbon with a double bond to this oxygen on the right we have only now one bond to oxygen right so we gained these two electrons because we increase the number of bonds to hydrogen so our other shortcut is to look at the number of bonds to oxygen like we talked about in the last example on the Left carbon has a double bond to oxygen so two bonds to oxygen on the right we have only one bond to oxygen so we decreased in the number of bonds to oxygen so that's a reduction again a fast way of figuring it out or we increased a number of bonds to hydrogen let's do one more of these problems so our goal is to figure out if our starting compound on the Left has been oxidized reduced or neither and this time these are the two carbons that we are going to analyze those the two carbons that have changed in this reaction so on the Left let's draw out what we have we have a carbon with a double bond to another carbon and both of those carbons are bonded to directly bonded to two more carbons on the right those carbons now only have a single bond between them and this carbon the left is bonded to a hydrogen this carbon on the right is directly bonded to an oxygen and let's put in those other carbons right we have another carbon-carbon bonds right let's put in those carbon-carbon bonds like that let's assign our oxidation states so we draw in our bonding electrons and we think about electronegativity differences but we're going to assume once again that our carbons have the same electronegativity on the left and so when we're assigning electrons let's just pick one of those carbons so let's pick the carbon on the Left right we divide up those two electrons in that bond give one electron to one carbon one electron to the other we do the same thing here and for the double bond with four electrons we divide up those four electrons we give two electrons to each carbon and so carbon is supposed to have four valence electrons and around it this carbon has one one two three and four so four minus four is an oxidation state of zero so this carbon has an oxidation state of zero same thing for the carbon on the right side of the double bond right it's in the same situation so it also has an oxidation state of zero what about for our product right let's examine those two carbons let's put in our bonding electrons so you draw in our bonding electrons here so you put those in a lot more bonding electrons to draw and we think about electronegativity differences right things have changed so now now let's focus in on the carbon on the left so the carbon the left is now bonded to a hydrogen and carbon is a little bit more electronegative so we give both of those electrons to carbon and then we have carbon bonded to carbon carbon bond to carbon and carbon bonded to carbon so what's the oxidation state of that carbon on the left now carbon is supposed to have four valence electrons and how many do we have around and see 1 2 3 4 5 so 4 minus 5 gives us an oxidation state of minus 1 so this carbon on the left now has an oxidation state of minus 1 what about the carbon on the right well we have a tie here right so we divide up those electrons a tie here but oxygen is more electronegative than carbon so oxygen gets both of those electrons so the carbon the right should have an oxidation state of 4 minus 3 here are the 3 electrons around carbon once we've accounted for electronegativity so that's an oxidation state of plus 1 so this carbon has an oxidation state of plus 1 so overall what happened here well let me use red so the carbonyl left went from an oxidation state of 0 to an oxidation state of minus 1 that is a decrease in the oxidation state so that carbon was reduced what about the carbon on the right side of the double bond that we started off with it started off with an oxidation state of 0 and it went to an oxidation state of plus 1 that's an increase in the oxidation state so that carbon was oxidized what can we say about the starting pound overall well the starting compound overall there's no net change in the oxidation states right so on the left for those two carbons we had a total of 0 on the right we had negative 1 and positive 1 for a total of 0 there's no net change so this would be neither the starting compound was overall it wasn't oxidized or reduced it's neither