I agree, this gave me a better understanding of the difference between the Sn reaction types.

chaemelion I agree. I’m a chemistry 1 high school student, so I don’t understand all of it, but it’s good info to have!

@@therainbowwillow4453 i am chemical engineering major currently...and i have leanrded a lot from nile ratjer from my proffessors

That explanation was amazing, I agree.

You would think so, but the ratios of which mechanism prevails is actually pretty close to 50/50. It all comes down to kinetics. Although the resonance stabilized carbocation is definitely very stable, the rate determining step is how quickly the H2O group spontaneously leaves. For SN2 reactions all it takes is the chloride coming in and attacking which happens much faster than the H2O leaving. So it’s almost a 50/50 mix. This illustrates the interplay between how kinetics, and resonance/sterics comes into play. From ones understanding of resonance, sn1 should be greatly favored and be the major product, but it’s fighting against the relatively slow process of the water molecule leaving. Whereas the sn2 attack by the chloride happens much faster before the resonance structure can be established.

@@spiderdude2099 correct me if my intuition is off here, but.. From what I understand, SN1 shouldn’t really happen here, since it‘s a terminal carbon atom, and even if you have a nice protic solvent the terminal carbocation should be waaaay too unstable. I don’t know to what degree the resonance structures would help, but in general terminal groups should always undergo SN2 reactions. Edit: just looked it up. Substitutions in the benzyl position will prefer SN1 if the benzyl group has electron-donating groups attached. As it is, the unsubstituted benzyl like seen here should prefer SN2.

@@moropikkuu the issue with that is that the stabilization given by resonance even by an unsubstitued benzyl ring is absolutely HUGE. Draw the resonance structures for the primary carbocation and you’ll see this. The charge is able to move to other carbons such that it leads to several resonance structures where the charge is on a secondary carbon. This greatly stabilizes it, and leads to SN1 occurring to a much greater degree than it should for being a primary carbon. The experimental results of performing SN1 vs SN2 reactions on benzyl halides comes out to around 50/50 because this effect is so strong. The effect of resonance can’t be overstated because, yes, you’re right as a primary carbon this should be much more dominated by SN2, but it’s not, they’re almost equal. It also has to do with kinetics. The resonance stabilized carbocation should actually make this reaction more SN1 than SN2, but the formation of the cation relies on the very slow kinetic step of water leaving and creating a charged carbon. Whereas SN2 doesn’t have this problem. It relies on nucleophilic attack which is a much faster kinetic step. This further leads to an equal split of the two mechanisms

Jesus, Bob.

Exactly right. The reaction conditions (polar protic solvent) in combination with the benzylic position bascially are screaming SN1.

Expect experimentally, the sn1 and sn2 mechanisms are almost 50/50 favored. The reason for this is due to kinetics. Although the carbocation has exceptional stability and would be expected to be the major product, it relies on the relatively slow step of the water spontaneously leaving. The SN2 reaction proceeds via an attack by the chloride which can happen much faster. Therefore the reaction mechanism is almost an even split. Sn1 is greater favored due to stability but hindered by a slow leaving step. The sn2 is fast with the attack by the chloride, but does not have the benefit of the stability of resonance. This illustrates the importance of kinetics for determining the experimental outcome of a reaction beyond theoretical expectations

Sn2 gets a stabilized transition state, don't forget that...

More theory definitely!

He called a benzylic carbon a primary carbon, I cringed. Totally agree with you.

Nabeel Chhatriwala Ha I subconsciously cringed as well! When I saw the positive charge on the aryl carbon group my mind was immediately imagining all the resonance structures available to stabilize the positive charge. Unfortunately I never got to the point of realizing the error in his rationalization of the predominant reaction mechanism occurring, but at least the right thought process was happening lol! oh well

It IS a primary carbon tho

Chris The Raven uhhhh, no. It’s a benzylic carbon. I suppose you could call it “secondary” but it’s quite different from aliphatic secondaries.

@@MisterLepton it's a carbon bound to another carbon. So, yes, it is primary.

+GhostyOcean I've been workin hard :)

no problem!

how did making meth go

Me too

​@@lifeonfire2390 me three

That's actually a good question. Basically, assuming by mix you mean dissolve both in water, the ions dissociate completely because the Ksp is high enough for KCl, KOH, NaCl, and NaOH. (If you haven't learned about equilibrium constants such as Ksp it might be good to look it up now.) So you just end up with a soup of K+, Na+, Cl-, and OH-. Usually when you have a reaction in the form of AB + CD > AD + CB it means one of the products is insoluble so it drops out of solution as a precipitate. For more information on that, look up double displacement reactions.

Alex I Dissolving in water was what I was initially picturing, yes, but only as a speculative starting point. I've heard of equilibrium constants, but I haven't delved into it all that deeply, and I think that might be a gap I'd wish to fill. Thanks!

Ha ha wonder what ur really trying to synth

+Random Experiments International I do use it. What is your tip? :)

+Nile Red First you draw everything as usual. Then you increase the size of the document. (File -> Document settings -> Layout -> Poster) I usually change it to 100 cm x 100 cm. Then I mark everything and make it as large as possible. I know it sounds a bit stupid, but when you save this document as a picture, the resolution is much higher :)

Cool, i never even thought of increasing the document size.

Yes lol it's interesting how he pronounces it. We Americans say "seevs"

Never encountered chloroacetone, but benzyl chloride is not as bad as chloropicrin, which feels like hot sauce in your eyes.

+TheBackyardScientist Damn!

Yeah the benzyl chloride was a bit less painful than getting soap in my eyes for a few hours.

+Nile Red ouch.

+Nile Red I stored like 75ml of this in a Pyrex reagent bottle, and opened it after a few days and as soon as I opened the cap it sprayed a mist out and freaked me out. I liked for the decomposition facts on it but couldn't find much. and it turned a muddy brownish red color. it was over molecular sieves also. any ideas on why? did it decompose? it was out of light but in a hot garage seeing how I really don't want it in my house. how long is the shelf life? I've tried finding lit on it but come up empty handed.

So is everything else on the planet

I knew your avatar looked familiar. Could it be fate...

Kronos DAW oh hai :D

I did. Symclosen (swimming pool), toluene and some radical starter for the polymerisation of styrene. Heating and reaction started. Use symclosen in some batches and every time new radical starter.

Huh?

That is true. I honestly kind of forgot to take solvent into account.

+MsMrVlog well the fact it is a primary alcohol which has an very stable carbocation by resonance in the phenyl proves a lot more the fact it is Sn1 than the polar protic solvent. Plus, in acid conditions, the protonation of alcohols yields a very good nucleofuge that favors Sn1 too.

+Michael Desgagne I know, but the solvent is just giving a small extra push which is worth mentioning

That is true

+Ben Sullivan That round bottom flask is tricky. From that angle, the stir bar disappears.

+Matt Luettgen Do you mean what does SN1/SN2 stand for? They literally mean Substitution nucleophilic 1 (unimolecular rate determining step) or 2 (bimolecular rate determining step)

+Raph Guenther In theory, but the amount of water present it crazy. You could generate HCl gas instead, but it is a lot of work for not that much gain

@@NileRed agreed.