Hydrohalogenation - Alkene Reaction Mechanism
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- čas přidán 12. 09. 2024
- Are you struggling with organic chemistry? Download my free ebook "10 Secrets To Acing Organic Chemistry" here: leah4sci.com/o...
leah4sci.com/o... presents: Alkene Reaction Mechanisms HYDROHALOGENATION, or the reaction of adding H-X to an alkene
This is the second video in my Alkene Reaction Mechanism series taking you step by step through the most common alkene reaction mechanisms focusing on the why and how in place of memorization
For questions and comments, find me on social media here:
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There are so many reaction mechanisms that I don't really remember the ones I learned when I took orgo. This is nice review.
So glad this helped!
May life be long and prosperous, Leah!
thank you!
I can just listen to your clear ochem gospel all day long
Why thank you very much!
Great explanation!! I sometimes struggle to understand who attacks who, but now looking at it this way I can picture it much easier than I expected. Thank you for this explanation!!
You're so welcome, I'm happy to share!
the carbocation argument is so much easier for me to understand/remember. thank you!
You're welcome!
I like your use of Markovnikov's idea here! It both plausibly explains these reactions and teaches us Markovnikov's rule. Both easier to use and more educational about Chem generally.
thank you :)
my professor has podcasts that were required to watch and their terrible! These videos are awesome. Thank you! I'm sure you have heard this before, but your a life saver.
Ugh, sorry about the terrible podcasts but glad I could help!
I'm currently a paying subscriber and her other paid videos make learning this way way better. These videos compliment them well but her other videos bring an added element to the learning experience.
Thank you for your kind words. I'm glad you are finding them helpful :)
What other paid videos?
Brian M. How much is it?
thank you so much i was so lost before you don't understand how grateful i am
You're very welcome, so glad it helped!
Thank you so much for the clarity of your videos!!
You are very much welcome. Don't forget to subscribe! :)
this video saved my life omg.
Wow, you give it too much credit! Always glad to help. :)
omg you are a star! watchingg the entire series
So glad you're liking the videos! Thanks :)
I become fan of your lecture mam....really helpful..the stereo-chemistry portion is really lucid and easy to memorize....Thanks a lot you..
You're very welcome, happy to help!
you are just making my organic chemistry easy to understand :) thanx
So happy to help!!!
@@Leah4sci Did you just reply to my comment after 9 years ?? wow hahah ....That's actually amazing 😂
Hey I love your work here but just an addition to this concept could you also show what products we would expect to get when we repeat the last reaction but with a hydride shift to it?
I just posted a new video on the hydrate shift reaction mechanism. I hope it helps
thanks a lot!!! you made my life so much easier :D keep making more videos :D You're awesome!
You're so very welcome!
It would be a good idea to also mention the idea of "hydride shifting" in this matter. At 6:55
even if someone drew the first intermediate with a secondary carbocation, one should always look if a shift of some type (hydride or alkyl) can occur that leads from a less stable carbocation to a more stable carbocation. The newly formed bond with the tertiary hydrogen can shift to the secondary carbocation, and leave a tertiary carbocation where the hydrogen previously was.
I didn't think of it when I recorded this video, but I have since recorded a more updated one showing the carbocation rearrangement via hydride shift
@@Leah4sci Hey! Thanks for replying! Nice to hear from you after 11 years xD. I attended one of your live sessions like back in 2012
The best of the bestsssss💗💗💗💗💗 thank youuuuu thank youuuuu
You're very welcome
I think you should reorganize your videos in the order things are taught in organic chemistry course because at the moment relevant videos were difficult for me to find. For example, the first part of your videos could be alkanes, chair formations, e-z, resonance, etc. Then the second part, could be alkenes, alkynes, mechanisms, NMR/IR stuff, Markovnikov, etc. If you do that, I think you could increase your views significantly.
While I haven't done that, you can use leah4sci.com/syllabus to help find my resources in order of the typical semester.
Thanks a lot, this have been really helpful. I am now able to remember each because they are so similar.
You're welcome, happy to help!
thank you very much Leah you made it simple
You're so welcome, happy to help!
Thanks ,you are my hero!
Awww, you're so welcome!
You are so great!! Thank you!
You're welcome!
Finally makes sense. Thank you so much!
You're so welcome, happy to help clear it up!
thank you! this was very easy to understand.
You're very welcome!
My daughter is struggling with o chem . As I liked the way you have explained in the video. I would like to know if you tutor her
Glad you enjoyed the video. I saw you email, did you get my reply?
Question. Would the attack from the halogen be considered a back side attack? meaning it would be facing the opposite direction from the hydrogen? (if forced to draw a dash-wedged diagram)
Love your method of explaining the mechanisms, I actually make Orgo videos as well. I really wish I had more time to put more videos up sometimes haha. Good luck with your future videos! =]
You've come a long way since then!
And can you also explain how we can expand the ring from 5 to 6 carbons using hydrohalogenation
A 6 carbon ring is most stable and so the intermediate will rearrange to give you the more stable version
Do you have a video on markovnikov's?
You can find resources on that and more at leah4sci.com/syllabus
Does the Hydrogen (7:52) go to the primary CH2? Thanks! Loving your videos!
Lovely as usual.
Thank you!
the last example is both regioselectivity and stereoselective
At which time in the video?
Hydrohalogenation is regioselective in that the product follow's Markovnikov's rule where the incoming nucleophile adds at the more substituted position.
This reaction is NOT stereospecific given that it undergoes a carbocation intermediate. Since carbocations are sp2 (flat) the incoming nucleophile can attack from either side giving you a racemic product
Ma'am in the last example that you explained in this video. Isn't the benzyl carbonation more stable than the 3° carbonation? So shouldn't the Br go to the c attached to the 3° carbonation.
At which specific point in the video? (Timestamp please)
amazing!!
thanks!
thank you very much
You're so welcome!
At 2:10, when a halogen gets a full octet, shouldn't the formal charge be zero?
No, the formal charge is -1 here. Halogens have 7 valence electrons, and when they gain a full octet, their formal charge is calculated by saying: 7 - 8 = -1
To learn more about formal charge, read about my shortcut at leah4sci.com/formal-charge-formula-and-shortcut/
thanks a lot..it's really help..
You're very welcome, happy to help
Would you also take into account stereochemistry when it is a chiral carbon? So for the HCL & HI example there would be two major products?
Yes, you could. The hydrohalogenation reaction produces a racemic mixture of syn and anti products. One stereochemical configuration is not preferred over the other. Showing both stereoisomers as products would be completely okay.
What video can I watch to help me identify what is the primary carbon and tertiary carbon?
I have a trick for classifying primary, secondary, and tertiary carbons in a molecule. You can find the relevant video on my tutorial at Leah4sci.com/Pencil
Hi Leah,
When doing an ionic addition to an alkene, how do you know when you will have a racemic mixture?
I'm sorry, but I don't offer tutoring through CZcams comments. For help with questions like this and more, I recommend you join the organic chemistry study hall. Details: leah4sci.com/join
Very great
Glad you like it, thanks for watching!
Thank you.
you are very welcome
I love you. I truly love you.
thanks!
i didnt understand why on the second example, the hydrogen went to the secondary carbon and then, on the cyclohexane example, the hydrogen went to the secondary and not the tertiary
We want to focus more on the position of the carbocation rather than on where the hydrogen goes. We want to form the more stable carbocation intermediate for a Markovnikov product. In the second example that begins at 2:50, the hydrogen is placed on the primary carbon, so that the carbocation formed is secondary. In the final cyclohexene example, the hydrogen happens to be placed on a secondary position, so that the more stable tertiary carbocation can be formed. For more on carbocation stability, make sure to see my tutorial at Leah4sci.com/carbocation
How are the able to identify which carbon is tertiary, secondary or primary on the starting material
its how many carbons attached to it. Basically 3 lines (makes it looks like a stick person without arms) tetiary (means 3 carbons). Double bond with a line? (its only technically 2 lines. secondary (2 carbon)). triple bond with a line attached.. guess what its still just two lines attached (secondary). Is it a part at the end with only one line but nothing on the other side? (that is primary carbon)
I have a great trick for this, which you can find on my site at leah4sci.com/pencil-trick-for-classifying-primary-secondary-and-tertiary-carbon-atoms/
Where can I find alkene preparation reactions?
I cover alkene prep reactions in various videos. See my alkene series and my SN/E series
8:11 won't there be a ring expansion?
If the carbocation forms on the primary carbon NEXT TO the ring then we have an option for ring expansion. However in this case there's nowhere for the carbocation to go and so the ring remains as 5 carbons
at 8:00 where did the Hydrogen go to?
The less substituted carbon as explained in the video
@@Leah4sci mam , is it possible that , hydrogen leave from 1 degree carbon . Because if i do that , ring expansion is possible . And 6 member ring is more stable than 5 member ring . So , leave the hydrogen from 1 degree carbon is more favourable or not .
Thank you mam
And sorry for my bad English
is this anti or syn addition?
Both. It's not stereoselective and will form a racemic mixture of products.
I cover this in my alkene cheat sheet: leah4sci.com/alkene-reactions-overview-cheat-sheet-organic-chemistry/
I love you Ms. :)
Aww thanks!
❤❤
Thanks for the positive feedback!