 hope you remember the reaction mechanism of an SN1 reaction. We talked about how the bond between the carbon and the leaving group breaks a carbocation forms and the attacking nucleophile swiftly attacks and forms the product right. Here we also talked about how the step one was actually the slowest step. This bond breaking was important for us because this step was the rate determining step. So if I want to make this reaction happen faster or if I want to increase the rate of the reaction I would have to do things that increase the rate of step one. So the factors affecting the rate of the reaction would be the carbocation stability more stable the carbocation more quickly it will form the leaving group stability. What if the leaving group is not stable alone it would want to attack the carbocation again and we won't get the product so it should be stable alone it should be happy alone so that it doesn't attack my carbocation again and there's a hidden factor it's the solvent we'll talk about it later. Hey does the nucleophile also affect the rate of the reaction well it clearly attacks in the next step so if it's not a part of the rate determining step it has no role to play in determining the rate of the reaction. So the strength and the concentration of the nucleophile they won't really affect the rate of the reaction. So let's focus on the carbocation stability factor. If I'm given a question where I get these two substrates and I'm asked which of the following would react the fastest via an SN1 reaction and I have to check what bond to break. In both the cases I can see how Cl- would actually leave. So what's the next thing that I should focus on? I should probably break the bond and see which carbocation would be more stable because the leaving group is the same. Let's do it these are the carbocations that I get right. Why don't you try comparing the stability of these carbocations before we do that together. In the first case I can see there are six alpha hydrogens while in the second case there are nine alpha hydrogens more the number of alpha hydrogens more is the hyper conjugation right and more is the stability. So the second carbocation is more stable than the first one and therefore the second substrate would react faster than the first one when we talk about the SN1 reactions. Let's take another example shall we. Here I have two cyclic substrates that are waiting to react via an SN1 mechanism. The leaving group is still the same it's still Cl- so let's just quickly make the carbocations in each case. These are my carbocations. Each neutral carbon atoms will form four bonds so if I count in the first case I can see four alpha hydrogens while in the second case I can see there are one two three four and three here seven alpha hydrogens again more the number of alpha hydrogens more is the stability and therefore the second substrate would react faster than the first one in case of an SN1 reaction. So let's quickly move on to the last example for the day. I have three substrates here and in each case I can see that the leaving group would be Pr- so what I really need to compare is the carbocation stability again. Let's form the carbocations and compare them try it yourself and then we'll do it together. Can I see alpha hydrogens here? Yes I can. In the first case there are six alpha hydrogens in the second case six again while in the third case there are three but is hyperconjugation gonna be the only factor here as well? I can see benzene rings can you? Is there a possibility of resonance? I can see a positive charge which is alternate to the pi bond. Let's try resonance then. So if I try drawing the resonating structures this is what I get. Oh so the positive charge is spread out in the entire ring so that happens in both the cases. Hey that helps me. So I can see that in the second and third case there's a stabilization via resonance and they also have alpha hydrogens six alpha hydrogens in the second one while three alpha hydrogens in the third one. So if I'm supposed to compare the stability in each case what do I do? Both have resonance but the second one has more alpha hydrogens so there's an overall extra stability that is provided to the second one as compared to the third carbocation right? So the second one is the most stable. What about the first one? There's no resonance there are just six alpha hydrogens. So the stability order would be and hence the rate would be as shown. More stable the carbocation the faster it will form and the faster would be the rate of reaction via SN1 for that particular substrate. In the next video we'll be talking about allylic, benzylic, vinylic and phenylic substrates and see whether they react via SN1 mechanism or not.