Aww HC, thank you very much for this comment. I made these for my students but glad you also found them helpful. I wish I had time now to make them better.
Great video, thanks for the clear and effective examples. On the worksheet linked in the description, why do examples f and h favor E2 over SN2? I thought due to NaOH being a small and strong base they would favor SN2, is it because they are too sterically hindered to do SN2 effectively?
Yes- when both SN2 and E2 are possible, secondary and tertiary alkyl halides favor E2 because of less sterics but also the stability of alkene being formed, over primary halide being favored for SN2
if h20 is given without temp then its sn1 and alchohol will give e1! in the question (e)(5th) . its ch3oh so here dielectric constant is less for it so it gives e1 and i guess it will not give sn1
Strong base weak nucleophile goes for E2 for tertiary. She said weak nucleophile but she also said strong base. However the strong base is too bulky to attack a carbocation, so that means it will attack a hydrogen which means elimination.
Great question! The effect of “hiding” the anion is much greater when the anion is acting as a nucleophile, rather than as a base (think of the solvent cage as making the Nu more sterically hindered). Therefore Sn2 will be more negatively impacted by protic solvent than E2. This might help: www.chemistrysteps.com/sn1-sn2-e1-e2-effect-of-solvent/
First of all thanks a lot for the great content. Second, for the (g) example I don't understand what happens in the Answer key. How do we know that is it only E1 and not SN1 ? Thanks
In the first question if KotBu is a poor nu then why is sn1 not happening as the nu isn't involved in the rate determining step of sn1 mechanism???? So it being a poor nu shouldn't stop sn1 from happening????
SN1 is not favored because type 1 reactions need a stable carbocation to form, but otBu is a charged species = no “patience” to wait for carbocation to form! Thats how we know it’s type 2.
Thanks for the video. Can someone explain to me why t-butoxide is a weak nucleophile? Nucleophile is a lone pair donor so shouldn't the oxygen be a good lone pair donor?
Hi Tushar! Yes - nucleophilicity and basicity are not exactly the same. Nucleophilic strength is based on kinetics - when nucleophiles are branched/bulky, the electron repulsion of these electron clouds create steric hindrance and slow down the reaction rate... thus tBuO- is a weaker nucleophile than OH- even though it's a stronger base than OH-. I hope this helps!
I go into it a little at around 10:15min mark of this video: ruclips.net/video/ivkquiO9Hgs/видео.html I also recommend this: www.masterorganicchemistry.com/2012/06/18/what-makes-a-good-nucleophile/
hello, thank you very much for this video! I have a question concerning exercice C, you said that if we had a chiral molecule we would make sure we changed the stereochemistry (R to S or S to R), but do we always necessarily do that or do we just change the relative configuration and see if that changes the stereochemistry??
HI Zoe! Thanks for your comment! Yes, you just change the configuration at the chiral center IF your nucleophile is attacking it at that precise carbon. So you don't have to label whether it's R or S, but just change it to the opposite configuration and make sure your drawing indicates that inversion of stereochem. For example, if you started with R-2-propyliodide, make sure it's S-2-propylwhatever at the end (or if it's wedged, make sure it ends dashed, or vice versa). However, please note that the chiral center may not be the carbon that is attacked - in which case, you would not change the chiral center! An example is R-1-bromo-2-methylbutane... after reaction with iodide, you should get R-1-iodo-2-methylbutane, because the chiral center is on carbon 2 and not carbon 1, where the nucleophilic attack is occurring! I hope this makes sense and that I answered your question but if not, please feel free to write back!
For example 2 is the product you crossed out not a minor product? Zaitsev is the most substituted alkene so why are the cis and trans alkenes considered minor products while the crossed out product is not?
Thank you ma'am. Just a question from the first problem- Will the poor nucleophile not wait for the formation of the carbocation? If yes, then it should be by E1 mechanism. Please reply ma'am, I'm preparing for NEET 2021 and sinking in variety of concepts.
Hi Soumya - right, if only there wasn't a strong base in the solution. Since tBuO- is a strong base, it will not wait for carbocation - it is very reactive and will start an E2 mechanism instead. So it's important to think of every reagent in terms of: strong Nu (favor SN2), weak Nu (favor SN1) AND ALSO strong base (favor E2), weak base (favor E1). Here we have tBuO- which is a weak Nu but strong base - E2 (faster) is favored over SN1/E1.
The key is understanding the reagent on top of the arrow. It’s a good Nu so it favors SN2 over SN1, and it’s a strong base which favors E2 over E1. Because it’s a secondary alkyl halide, both are possible. The chart on this page from Klein might help you with knowing whether the reagent is a strong or weak Nu and strong or weak base: www.bartleby.com/solution-answer/chapter-1010-problem-1027p-organic-chemistry-as-a-second-language-first-semester-topics-4th-edition/9781119110668/cd1360b4-5079-11e9-8385-02ee952b546e
Hi I would like to ask if you mind tutoring me online on organic chemistry of rxns and aromaticity including E1,E2, SN1,SN2, electrophilic addition, radical substitution, alkenes, and alkynes rxns .....etc ? if so can you please give me any contact info. Thanks
Actually E2 is favored in protic solvent- that is a big difference between E2 and SN2. Further reference about this: www.masterorganicchemistry.com/2012/12/04/deciding-sn1sn2e1e2-the-solvent/
how do you know what will qualify as steric hindrance? what if the attraction energy of the attacking molecule is high enough to overcome it (bend the bonds of the existing geometry of the attacked molecule)? this shit is why organic chemistry is 90% hand-waving garbage.
Hi Rick - we can get quantitative if you want, but most of the organic chem at this level is presented qualitatively to keep it accessible (I think). We try to recognize patterns from the data but I agree that omitting these data lead to feelings of hand-wavyness... Yes - I can understand your point. In general, what qualifies as enough steric hindrance to predict "no reaction" is going to be where the nucleophilic carbon is tertiary (and in some cases, secondary, or next to a tertiary carbon). I usually see 99.9% examples where something considered "branched" (isopropyl, isobutyl, or in a cyclic ring like DBN) to be hindered enough to predict no reaction or at best, minor products. We could get into the weeds on this and look up research articles siting repulsion energies if you'd like, but most treatments of this material remain qualitative. Advanced organic chem texts will go more into more detail.
@@orgotime6196 i appreciate your reply, but this is the problem with all of western STEM education, we dont teach from first principles. after youve had OC and memorized the hand-waving, you have to unlearn it all and start from scratch having wasted another year of your life. i'm not blaming you or your channel, i'm saying the whole subject is a useless waste of time that purely serves as a filter class. same with linear algebra. either teach by historical development, or teach by first principles (whatever those are in present era.) /rant
![SN1 SN2 E1 E2 Pre-Finals Practice [Live Recording] Organic Chemistry Review](/img/1.gif)
You are the first one explaining it in a way that I can finally understand it, thank you so much
I like how our instructor makes us answer those types of things without him ever mentioning Sn 1, Sn 2, E1 and E2. So new to my ears!
I came back to this video because I wanted to say thanks!!! You're a legend, here's a virtual high five :) 🖐
Aww HC, thank you very much for this comment. I made these for my students but glad you also found them helpful. I wish I had time now to make them better.
I like ur flow chart ,I never fail in attempting ctq.Thank u
Most underrated channel on organic chemistry...
Thank you ma'am. Love ❤from INDIA🇮🇳
Ahh yes, the memories from orgo. Hands down one of the best professors I've taken!
Aww Mohammad! I miss you. You always asked great questions in class, and I enjoyed our hiking trip that summer!
Where have you been all my life!!!
This was SO incredibly helpful, THANK YOU!
Great video, thanks for the clear and effective examples. On the worksheet linked in the description, why do examples f and h favor E2 over SN2? I thought due to NaOH being a small and strong base they would favor SN2, is it because they are too sterically hindered to do SN2 effectively?
Yes- when both SN2 and E2 are possible, secondary and tertiary alkyl halides favor E2 because of less sterics but also the stability of alkene being formed, over primary halide being favored for SN2
if h20 is given without temp then its sn1 and alchohol will give e1! in the question (e)(5th) . its ch3oh so here dielectric constant is less for it so it gives e1 and i guess it will not give sn1
Thank you from Korea 🇰🇷
Thanks a lot how do I get the full pdf is glimpse was amazing
Thanks from INDIA 🙌
Your vedios are great! I love 'em
For the first problem (a) you said it won't do sn1 because of poor nu , but doesn’t sn1 prefer weak nu?
Strong base weak nucleophile goes for E2 for tertiary. She said weak nucleophile but she also said strong base. However the strong base is too bulky to attack a carbocation, so that means it will attack a hydrogen which means elimination.
This is extremely helpful
If rick and morty’s summer became a chemist
Thanku
this concepts are so confusing... but this video has helped me a lot. Thanks
So well done! Thank you, this was fun!
@nicholas - thank you so much! You are very kind!
So Helpful! Thank you!!
Thank you for this video, but how does protic favor E2? Wouldnt it also “hide” the base, making it less likely to remove an H+
Great question! The effect of “hiding” the anion is much greater when the anion is acting as a nucleophile, rather than as a base (think of the solvent cage as making the Nu more sterically hindered). Therefore Sn2 will be more negatively impacted by protic solvent than E2. This might help: www.chemistrysteps.com/sn1-sn2-e1-e2-effect-of-solvent/
miss why did we say that E1 favors Zietsev olefine while we are going to get a racemic mix?
First of all thanks a lot for the great content. Second, for the (g) example I don't understand what happens in the Answer key. How do we know that is it only E1 and not SN1 ? Thanks
Thank you!!!!
Thank you
hi, is there any way so that I can get this workbook?
Where can I found this pdf
In the first question if KotBu is a poor nu then why is sn1 not happening as the nu isn't involved in the rate determining step of sn1 mechanism???? So it being a poor nu shouldn't stop sn1 from happening????
one year later reply lol it's because DMSO is a polar aprotic solvent sothere will be no solvatation
SN1 is not favored because type 1 reactions need a stable carbocation to form, but otBu is a charged species = no “patience” to wait for carbocation to form! Thats how we know it’s type 2.
Thanks. Subscribed
How to get the full pdf of this WS?
Can U plz Provide this Pdf ???
can you provide notes
link....
how can i get these notes?
How is OH a weak Nu in problem E but all of a sudden a strong Nu in problem H???
THANK YOU SO MUCH FOR THIS
Thanks for the video. Can someone explain to me why t-butoxide is a weak nucleophile? Nucleophile is a lone pair donor so shouldn't the oxygen be a good lone pair donor?
Hi Tushar! Yes - nucleophilicity and basicity are not exactly the same. Nucleophilic strength is based on kinetics - when nucleophiles are branched/bulky, the electron repulsion of these electron clouds create steric hindrance and slow down the reaction rate... thus tBuO- is a weaker nucleophile than OH- even though it's a stronger base than OH-. I hope this helps!
In b.)
Isn’t it about Sayzeff / Hofmann rule or something like that? ^^‘
So for question should it favor Hoffman reaction since we have a bully base
Question B
Thank you Ma'am, Is there any info on how to know which nucleophile is good or bad?
I go into it a little at around 10:15min mark of this video:
ruclips.net/video/ivkquiO9Hgs/видео.html
I also recommend this:
www.masterorganicchemistry.com/2012/06/18/what-makes-a-good-nucleophile/
Hello, may I ask if the reaction between benzyl chloride and sodium actetae is SN1 or SN2 reaction? thx
What is the book?
THANKYOU SOOO MUCH :))))))))))
hello, thank you very much for this video! I have a question concerning exercice C, you said that if we had a chiral molecule we would make sure we changed the stereochemistry (R to S or S to R), but do we always necessarily do that or do we just change the relative configuration and see if that changes the stereochemistry??
HI Zoe! Thanks for your comment! Yes, you just change the configuration at the chiral center IF your nucleophile is attacking it at that precise carbon. So you don't have to label whether it's R or S, but just change it to the opposite configuration and make sure your drawing indicates that inversion of stereochem. For example, if you started with R-2-propyliodide, make sure it's S-2-propylwhatever at the end (or if it's wedged, make sure it ends dashed, or vice versa). However, please note that the chiral center may not be the carbon that is attacked - in which case, you would not change the chiral center! An example is R-1-bromo-2-methylbutane... after reaction with iodide, you should get R-1-iodo-2-methylbutane, because the chiral center is on carbon 2 and not carbon 1, where the nucleophilic attack is occurring! I hope this makes sense and that I answered your question but if not, please feel free to write back!
@@orgotime6196 Okay thank you very much for your explanations!!
This helped thanks!!!!
For example 2 is the product you crossed out not a minor product? Zaitsev is the most substituted alkene so why are the cis and trans alkenes considered minor products while the crossed out product is not?
Nice video! I'm trying to do the same with my channel for my ochem class at Northeastern University!
Hi Steven! That's great - I'd love to check it out!
can i get a copy of that book
good day, how can I get those pdf to as reference?
I mean the notes pdf
Starship
Thank you ma'am. Just a question from the first problem-
Will the poor nucleophile not wait for the formation of the carbocation? If yes, then it should be by E1 mechanism. Please reply ma'am, I'm preparing for NEET 2021 and sinking in variety of concepts.
Hi Soumya - right, if only there wasn't a strong base in the solution. Since tBuO- is a strong base, it will not wait for carbocation - it is very reactive and will start an E2 mechanism instead. So it's important to think of every reagent in terms of: strong Nu (favor SN2), weak Nu (favor SN1) AND ALSO strong base (favor E2), weak base (favor E1). Here we have tBuO- which is a weak Nu but strong base - E2 (faster) is favored over SN1/E1.
@@orgotime6196 Thank you so much maam...
The last example was very hard to understand, I still don't get it..
The key is understanding the reagent on top of the arrow. It’s a good Nu so it favors SN2 over SN1, and it’s a strong base which favors E2 over E1. Because it’s a secondary alkyl halide, both are possible. The chart on this page from Klein might help you with knowing whether the reagent is a strong or weak Nu and strong or weak base:
www.bartleby.com/solution-answer/chapter-1010-problem-1027p-organic-chemistry-as-a-second-language-first-semester-topics-4th-edition/9781119110668/cd1360b4-5079-11e9-8385-02ee952b546e
Hi I would like to ask if you mind tutoring me online on organic chemistry of rxns and aromaticity including E1,E2, SN1,SN2, electrophilic addition, radical substitution, alkenes, and alkynes rxns .....etc ? if so can you please give me any contact info. Thanks
Hi Dr Kora, sorry I am only getting your message now! If it’s not too late you can email me: gershie@gmail.com
Bulky*
u made a mistake e2 is favored when aprotic not protic idk if u miss spoke but i wanted to point it out for anyone watching
Actually E2 is favored in protic solvent- that is a big difference between E2 and SN2. Further reference about this:
www.masterorganicchemistry.com/2012/12/04/deciding-sn1sn2e1e2-the-solvent/
algorithms brought me here
you didn't do part d
you really gonna skip all those rings? :(
s
how do you know what will qualify as steric hindrance? what if the attraction energy of the attacking molecule is high enough to overcome it (bend the bonds of the existing geometry of the attacked molecule)? this shit is why organic chemistry is 90% hand-waving garbage.
Hi Rick - we can get quantitative if you want, but most of the organic chem at this level is presented qualitatively to keep it accessible (I think). We try to recognize patterns from the data but I agree that omitting these data lead to feelings of hand-wavyness... Yes - I can understand your point. In general, what qualifies as enough steric hindrance to predict "no reaction" is going to be where the nucleophilic carbon is tertiary (and in some cases, secondary, or next to a tertiary carbon). I usually see 99.9% examples where something considered "branched" (isopropyl, isobutyl, or in a cyclic ring like DBN) to be hindered enough to predict no reaction or at best, minor products. We could get into the weeds on this and look up research articles siting repulsion energies if you'd like, but most treatments of this material remain qualitative. Advanced organic chem texts will go more into more detail.
@@orgotime6196 i appreciate your reply, but this is the problem with all of western STEM education, we dont teach from first principles. after youve had OC and memorized the hand-waving, you have to unlearn it all and start from scratch having wasted another year of your life.
i'm not blaming you or your channel, i'm saying the whole subject is a useless waste of time that purely serves as a filter class. same with linear algebra. either teach by historical development, or teach by first principles (whatever those are in present era.)
/rant
@@rickdeckard1075A lot of the time that isn’t practical for career considerations and different needs of students
@@coolexplorer1015 yes thats why they cant get and keep a job that doesnt require being told what chem to put in what testtube
hi nicely explain
plz tell from where i get worksheet
@sanjuwaves
Osm
THANK YOU SO SO MUCH FOR THIS