7 Distinguishing Between SN1, SN2, E1, and E2

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Ive been performing poorly all semester with my old school Orgo professor. I even contemplated dropping the course because it was seemingly a different language to me. Then I found out about your videos and purchased a subscription on your website. Thanks to you, the content became so much more understandable and my grades improved immediately. This is definitely a course that made me question if I still wanted to apply to Dental school. After studying your videos, I am right back on track with my ultimate goals. You do a phenomenal job helping us understand and enjoy organic chemistry. Thank you so much man you are literally a life and GPA saver.

[@ChadsPrep]

This is gratifying to hear, TyShawn - glad you are seeing results. Keep up the hard work and you'll keep enjoying success. Thanks and Happy Studying!

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This is quite literally the best video I’ve found on this topic. Thank you so much for going into so much detail. I feel less stressed already!

[@ChadsPrep]

Glad it was helpful for you Elise!

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[@ChadsPrep]

Thanks Kubensis...very high praise indeed. Glad you're finding these helpful!🙂

[@SewueseVivian]

Exactly what was going through my mind. Finding this was worth it.

[@adrianj9695]

Thank you so much for these free videos. You've helped clarify all 4 of these mechanisms so well. I feel much more confident about them now.

[@ChadsPrep]

You're welcome, Adrian!

[@DiyaHimanshuPatel]

this is the best simplified explanation of substitution and elimination reactions. Thank you so much!!

[@ChadsPrep]

You're welcome!

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This was incredibly helpful. Thank you. Now I feel like I actually grasp this (an hour before the exam) I’ll let y’all know how it goes.

[@ChadsPrep]

Fingers crossed!

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Awesome Tracy! Glad you're finding it helpful!🙂

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[@ChadsPrep]

Glad you found the channel, Nyctora - hope you do well on your exam.

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i have an exam today and this video's chart absolutely SAVED me, tysm. I'll definitely be translating these vids for my friends.

[@ChadsPrep]

Glad to hear it - hope you do well on your exam!

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This was so amazing. I think i can now go to write my exams with a calm mind. Thank you so much Chad's Prep for being amazing ❤️

[@ChadsPrep]

You're welcome and Thank You.

[@DucksOnQuack121]

I’m like 5 minutes in and my exam is in 2 hours but this is 100% a good video already for getting straight to the point needed (with some tricks)

[@ChadsPrep]

Hope you did well, Brandon!

[@ghostkidgamerez3917]

Hi Chad! How come at 7:51, you don't worry about the Br being antiperiplanar to the Hydrogen because its a E2? And doesn't 2(degree symbol) have priority over 1(degree symbol) in E2?

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We love you, Mr. Chad

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What a queen. A life savior

[@ChadsPrep]

Glad the video helps!

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Sir thank u so much , ur a saviour .

[@ChadsPrep]

You're welcome Alma! So glad you're finding these helpful!

[@thebeastsharma6352]

Very much helpful. Namastey from India 🇮🇳👋🙋‍♂️

[@ChadsPrep]

Thanks.

[@adityachaudhary6729]

Superb explanation 🙂 love from india ❤️

[@ChadsPrep]

Thanks from USA!

[@ARVINMONTEDERAMOS]

at 6:10, since there is an applied heat in the reaction, doesn't that mean it would prefer proceeding with the elimination reaction only?

[@jmac5501]

Chad you are the GOAT

[@ChadsPrep]

Thanks!

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I literally love this guy.

[@ChadsPrep]

@@tyshawnharris5959 Excellent!!

[@pasutto-ying847]

Thank you, you make it clear

[@ChadsPrep]

You're welcome Pasut! Glad you found this lesson helpful!

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[@ChadsPrep]

Glad to hear it!

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[@ChadsPrep]

Your'e welcome - Happy Studying!

[@Dwooswa]

a little feedback: add some compression to your voiceover so that audio levels are the same volume throughout the whole video. Thanks for the clutch study help!

[@ChadsPrep]

You're welcome and thanks for the feedback.

[@badshahthind7412]

Sir you are awesome 😍😇

[@ChadsPrep]

Thank you!

[@Lilacbutterfly20]

In your first example, you just said it would be sn1/e1 but what if I need to choose which reaction it would be? How would I go about finding out which one that is?

[@ChadsPrep]

SN1 and E1 are difficult to distinguish from one another and under most conditions you get a significant amount of both occurring. However, some textbooks and professors will emphasize that E1 will be favored at higher temperatures. If your professor has made a point of this go with it. Hope this helps!

[@cyrilbinoyskariah3109]

sir but what about for polar protic , aprotic and non polar solvents, in that case how to choose sn1, sn2 , e1,e2????????

[@ChadsPrep]

In theory the solvent will have less importance in determining which mechanism or mechanisms are likely, but in practice if you're performing these reactions in the lab then you should definitely pay attention to your solvent. I do discuss the role of the solvents in the earlier lessons in this section: how SN1 and E1 reactions must have a polar protic solvent, and how E2 reactions are faster in polar aprotic solvents but work just fine in polar protic solvents too. It is the SN2 reactions where we often oversimplify the picture because reality is more complex than we want to explain to students. Most SN2 reactions strongly prefer polar aprotic solvents. Many textbooks and professors will say nothing more on the topic, but some will go further getting closer to the truth. I stopped here in the lesson as that is what will be required of the majority of students. But the truth is that smaller nucleophiles (from period 2 on the periodic table) that are negatively charged (most strong nucleophiles are) typically require the solvent to be polar aprotic. But larger nucleophiles (period 3 and below) will typically still react faster in polar aprotic solvents but tend to work just fine in polar protic solvents too. And the last level of complexity is that neutral nucleophiles (there aren't too many strong nucleophiles that aren't negatively charged) actually react faster in polar protic solvents, but I've only seen one textbook that even presents this. So now you've got something closer to the truth and perhaps your professor is requiring more out of you here than the average student than you're asking about it. But 90% of the time you can probably determine the mechanism by an examination of the just nucleophile and substrate. But if you do look at the solvent you could make the following generalizations: Polar aprotic solvent --> SN1 and E1 are not possible so the mechanism will be SN2 and/or E2 Polar protic solvent --> More likely to be SN1 and E1, but that doesn't have to be the case as most E2 reactions work just fine in polar protic solvents and some SN2 reactions work in polar protic solvents as well. And I didn't mention it but you are not likely to see nonpolar solvents entering the discussion as they are not appropriate for substitution and elimination reactions. They don't form ion-dipole interactions which means they can't stabilize carbocations so no SN1/E1 and the majority of strong bases and nucleophiles, being ionic, won't be soluble in nonpolar solvents so no SN2/E2. Hope this helps and happy studying!

[@jumanaalomary7895]

anyone know if Chad has a book or notes that I can print ?

[@ChadsPrep]

Hey Jumana. 168 page study guide and reaction summaries are included in my Ultimate Organic Chemistry Review on ChadsPrep.com. Happy Studying!

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[@asudharani9235]

Sir.how can u be my ochem tutor?

[@ChadsPrep]

I'm not presently doing any private tutoring, but I do have a robust organic chemistry prep course available at www.chadsprep.com! Happy Studying!

[@loygebaguio6468]

i hope he just write a full mechanism