• Set Yourself Up For Success Webinar

    October 6, 2021 at 2 PM Eastern/11 AM Pacific
    SDN and Osmosis are teaming up to help you get set up for success this school year! We'll be covering study tips, healthy habits, and meeting mentors.

    Register Now!

  • Funniest Story on the Job Contest Starts Now!

    Contest starts now and ends September 27th. Winner will receive a special user banner and $10 Amazon Gift card!

    JOIN NOW
  • Site Updates Coming Next Week

    Site updates are coming next week on Monday, Wednesday, and Friday. Click the button below to learn more!

    LEARN MORE

Diels Alder Help!

BiomajorPreDent

Senior Member
10+ Year Member
Dec 18, 2008
653
3
0
  1. Dental Student
Okay, I might be a bit anal here..but on destroyer 76 (2009 ed) I just noticed that the molecule is locked in S-Trans form.

I have this exact structure in my ochem textbook and it says that this will not react when its locked in S-Trans..it only works if its S-Cis

But destroyer shows a 1,2 addition and makes no mention of its S-Trans form

Can someone shed some light on this? :confused:
 

UCB05

Full Member
Jun 14, 2009
800
3
0
  1. Pre-Dental
I dont have the 2009 edition of destroyer. The point about the Diels-Alder reaction is that the diene has to be able to react in the cis conformation because the transition state and product is a cyclohexene ring. The cis/trans geometry of the dienophile does not inhibit the reaction though. That just determines the conformation of the substituents in the product.

I don't know where a 1,2 addition that you mention comes in. Are you talking about a different reaction mechanism, maybe?
 

Shinpe

Full Member
May 22, 2009
341
0
51
  1. Dental Student
Hmm I have the jan 2009 version. Are you talking about the one that says "predict the product at -40 for..."? This is not a Diels-alder reaction. This is just a electrophilic addition of HCl to a conjugated diene. Since it's at -40, it's gonna be under kinetic control and give 1,2-addition while at higher temperatures, it would give 1,4-addition under thermodynamic control.
 

BiomajorPreDent

Senior Member
10+ Year Member
Dec 18, 2008
653
3
0
  1. Dental Student
I dont have the 2009 edition of destroyer. The point about the Diels-Alder reaction is that the diene has to be able to react in the cis conformation because the transition state and product is a cyclohexene ring. The cis/trans geometry of the dienophile does not inhibit the reaction though. That just determines the conformation of the substituents in the product.

I don't know where a 1,2 addition that you mention comes in. Are you talking about a different reaction mechanism, maybe?

Yes, I got this confused with the Diels-Alder

Hmm I have the jan 2009 version. Are you talking about the one that says "predict the product at -40 for..."? This is not a Diels-alder reaction. This is just a electrophilic addition of HCl to a conjugated diene. Since it's at -40, it's gonna be under kinetic control and give 1,2-addition while at higher temperatures, it would give 1,4-addition under thermodynamic control.

Holy crap! You are right I am so dumb..and I got this correct when I did it, but I was just browsing through really fast and was like wait a minute....s-trans?

Thanks!!
 
About the Ads

Sublimation

Full Member
10+ Year Member
5+ Year Member
Jun 14, 2008
574
0
101
  1. Pre-Dental
Just know that under kinetic control you want the intermediate with the lower activation energy the secondary carbocation, giving rise to the 1,2 addition. while on the other hand with thermodynamic control you will get the more subst. product and more stable produc the 1,4 addition.
 
This thread is more than 12 years old.

Your message may be considered spam for the following reasons:

  1. Your new thread title is very short, and likely is unhelpful.
  2. Your reply is very short and likely does not add anything to the thread.
  3. Your reply is very long and likely does not add anything to the thread.
  4. It is very likely that it does not need any further discussion and thus bumping it serves no purpose.
  5. Your message is mostly quotes or spoilers.
  6. Your reply has occurred very quickly after a previous reply and likely does not add anything to the thread.
  7. This thread is locked.