 hyper conjugation like I effect or resonance it is also classified into two categories plus H effect and minus H effect. Plus H effect are shown by electron releasing group electron releasing group. So in short we also call it as E R G electron releasing electron donating anything you say minus H groups are electron withdrawing is shown by electron withdrawing group which is nothing but E W G right. So all those groups which can release electron are known as plus H are known to be shown plus H effect groups which are electron withdrawing in nature are said to be shown minus H effect. So one by one we will discuss this plus H and minus H. The first example first one we are taking here is plus H effect plus H effect for example you see I am taking this toluene. So this is an example of what hyper conjugation in alkene alpha carbonate is this and we have three alpha hydrogen present. So when I draw the hyper conjugative structure this sigma converts into pi and this pi converts into lone pair. So we get this H plus further you see if you draw the resonating structure here right then a number of hyper conjugative structure here we can draw that is equals to again the number of alpha hydrogen. So in this example you see what happens due to this hyper conjugation these are electron releasing group right it releases this electron into the benzene ring okay. So in this course what happens the ortho and para position will get the negative charge okay. So the benzene ring becomes electron rich now and what position the electron density is more now position is ortho and para position. So what we can write here we can conclude from this that due to plus H plus H effect the benzene ring becomes becomes electron rich ortho and para position right. So what happens another thing meta position meta position does not get affected does not get any effect by this okay. The only ortho and para position becomes electron rich okay. Now one important comparison we have if you compare the electron releasing nature of this group CH3 CD3 and CT3 electron releasing nature of this group we know the I effect of this is maximum then this and then this right TDH I effect plus I effect okay but when we talk about hyper conjugation plus H it is more for CS3 then CD3 and then CD3 right CH3 CD3 and CD3. The reason behind this is what like I have already discussed if you compare the bond length of all this group bond length it is maximum for CH and then CD and then CT bond length order is this okay. So maximum bond length we have here so this bond CH bond is the weakest hence easy to break comparatively okay and we know hyper conjugation in which the sigma bonds breaks and it converts into pi bond the more easier like if the bond energy is less it is easy to break that bond which increase the tendency of hyper conjugation that is why CS3 shows maximum hyper conjugation among the three. However if you consider the plus I nature of these groups the order is reversed okay the small difference here must keep in mind this is very important okay because we know hyper conjugation is more dominating effect okay that is why this comparison is important okay. So the point here you have to memorize is because of hyper conjugation plus H effect the ortho and para position in the binging ring becomes electron rich okay. So now the next thing we are going to discuss is minus H effect in minus H effect like I said it is electron withdrawing group if I compare these three CF3, CCL3, CBR3 and CI3 in all these four groups only CCL3 shows minus H effect minus H effect this won't show minus H this won't show minus H this won't show minus H why it does not show because in carbon and fluorine the bond energy is very high okay. So I will write down one line just carbon and fluorine bond energy because of a small size bond energy is very high right for CBR and CI these two the electronegativity difference between carbon and bromine and carbon iodine is not that much is very small that is why minus H effect is not possible in all these three molecules but all these three molecule shows minus I okay so I will write down here this also shows minus I minus I and minus I minus H they will not show minus H is only shown by CCL3 okay. So now what happens with this minus H effect in the benzene ring for example you see CCL, CL and CL right minus H effect this pi converts into pi and sigma goes here on the chlorine. So that is hyper conjugative structure is this right for the hyper conjugative structure resonance structure if you draw this pi electron comes over here and it forms a positive charge here double bond double bond double bond and CL okay. So with this another hyper conjugative with another resonance structure of this we can draw but that is not our concern okay. Again the point is what because of minus H effect the benzene ring becomes electron deficient okay because you see an electron deficient at what position ortho and para position okay. So because of minus H effect what we can say that the benzene ring becomes electron deficient at ortho and para position but the meta position is not affected by this hyper conjugation or minus H effect. So here I write down due to minus H effect the benzene ring becomes electron deficient electron deficient at ortho and para position. In other way what we can say that the meta position is become electron rich here the meta position is electron rich. So any electrophile if it is attacked onto this ring the tendency for that electrophile to attack onto the meta position is maximum or more right. So next thing we will write meta position does not get affect minus H effect okay. So this is what you have to understand that whether the benzene ring is becoming electron rich or becoming electron deficient okay. Few examples I will write down we have to find out the order of electron density in the benzene ring whether it is decreasing or increasing. You see all these examples we have to find out the order of electron density in the benzene ring okay in which of this molecule the electron density is more in the benzene ring okay. Now you see this CS3 it shows what plus H and this OCS3 shows plus M right. So mesomeric effect or resonance effect is dominating over hyper conjugation electron density will be rich in the second molecule. CCL3 minus H and O2 minus M OCS3 plus M CS3 plus H okay. So electron density in the benzene ring is increased by plus M or plus H effect okay and decreased by minus M or minus H effect. So if you write down the order of electron density in the benzene ring it will be maximum for this because plus M is the most dominating effect we have here. Then we have plus H because both are electron like the both effects increases the electron density in the benzene ring. Then we have minus H and minus M minus H will decrease the electron density but this decrease is lesser than the decrease in case of minus M effect. So first second third and fourth the order of here you see this molecule shows minus H and here minus H minus I but minus H is not possible because it is at meta position okay. So only minus I effect will be there but minus H is more dominating and what is what kind of effect is this minus H and minus I these are electron withdrawing the electron density will decrease here more than this hence the more electron density in case of second molecule okay because minus H is dominating effect here. CCL3 both will show minus H right here it will show minus H but only one group so electron density is more in the second case. CF3 shows minus I and this also shows minus I okay it depends upon right. So actually this molecule is same I will just make one change here okay I have written CF3 only I will make one change here I will just write it down CBR3 both shows minus I right but the minus I effect of CF3 is more so this molecule will have more electron density okay. So this is how we compare okay the order of hyper conjugation inductive effect and resonance always plays a role into all this you know type of questions and the effect is what resonance is more dominating than hyper conjugation than I effect okay. So according to that we will consider the electron density in the benzene ring okay plus M effect has more tendency to release electron okay so plus M is the most dominating effect we have whenever we have plus M then electron density will be maximum over there okay whenever we have minus M the electron density will be minimum over there okay right suppose in this question I have plus M minus M plus H minus H right so both positive effect that you have that will increase the electron density okay and negative effect decrease the electron density so obviously both positive one is more than these two the electron density if you are considering on the benzene ring and mesomeric effect is the most dominating effect so maximum we have plus M minimum we have minus M second position we have plus H third position we have minus H okay that is how the order is written here