Basic Orgo questions. Help Please!

[Doa110]

---

Members do not see this ad.

These may be easy concepts for you, but I’m making lots of mistakes when doing the test and finding the final product of some reactions. PLEASE HELP!

1) How do we know, in a reaction, when we have to apply Markovnikove rule? When is it Anti-Mark? I know how it works (H-goes to the carbons with more H….) I don’t know when it’s Mark, and when it’s Anti?
ex: With H-X, Br2, Cl2 how the substitution/addition takes place in alkenes, or cycloalkenes? Cl2 is added to the ring only in 1,2 addition?

2) As a general rule Arenes follow Electrophilic addition, so If the arene is unbranched, then the addition takes place on the ring. right? If it’s substituted by e-withdrawing groups, and/or e-donation groups, how does the reaction takes place? Is it through nucleophilic substitution?

 

[klutzy1987]

2) You have to look at what reagents are used to do the substitution, certain reagents add to the ring like FeBr3 while others add to the branching like NBS. It depends on the reagents, not on the substituents on the ring.

 

[nitrolegs]

These may be easy concepts for you, but I’m making lots of mistakes when doing the test and finding the final product of some reactions. PLEASE HELP!

1) How do we know, in a reaction, when we have to apply Markovnikove rule? When is it Anti-Mark? I know how it works (H-goes to the carbons with more H….) I don’t know when it’s Mark, and when it’s Anti?
ex: With H-X, Br2, Cl2 how the substitution/addition takes place in alkenes, or cycloalkenes? Cl2 is added to the ring only in 1,2 addition?

2) As a general rule Arenes follow Electrophilic addition, so If the arene is unbranched, then the addition takes place on the ring. right? If it’s substituted by e-withdrawing groups, and/or e-donation groups, how does the reaction takes place? Is it through nucleophilic substitution?

1) this is what i went by: most reactions follow markov, so when in doubt follow markov. there are only a couple exceptions: hydroboration (OH goes on the least substituted carbon) and radical bromination (most stable radical is formed). i know there are more but i forgot them already😕

 

[dmd4u]

Any reagants where there is a peroxide (ROOR) or hydroboration are both anti-markovnicov.. Most everything else it seems in marcov..

 

[Doa110]

Thanks guys!
Can you please give me more details/reagents for number #2?

 

[klutzy1987]

Crack out a textbook and study the section on aromatics, it is supremely imoprtant and would be silly to think thatbyou can learn the entire chapter from the message board here. Any specific questions ill be glad to help but first you need to read it and learn the reactions, or at least go over a destroyer roadmap.

 

[appleonius]

2. http://en.wikipedia.org/wiki/Electrophilic_aromatic_substitution

 

[Dotoday]

Ok, Markovnikov rule- H goes to the Carbon with the most H`s. You use Markovnikov rule when you are in acid. Acid creates carbocations. For example alkenes with H2SO4, HCl, HI, HBr - react markovnikov.
Antimarkovnikov- you put H to the carbon with the least number of Hydrogens. HBr and ROOR puts Br antimarkovnikov. However, this only works with HBr. HCl and ROOR will still put Cl markovnikov. ALso, H2SO4 and water puts OH markovnikov. However, 1)BH3 THF,
2)H2O2 and OH-
will put OH antimarkovnikov.
Hope this helps.

 

[Doa110]

Ok, Markovnikov rule- H goes to the Carbon with the most H`s. You use Markovnikov rule when you are in acid. Acid creates carbocations. For example alkenes with H2SO4, HCl, HI, HBr - react markovnikov.
Antimarkovnikov- you put H to the carbon with the least number of Hydrogens. HBr and ROOR puts Br antimarkovnikov. However, this only works with HBr. HCl and ROOR will still put Cl markovnikov. ALso, H2SO4 and water puts OH markovnikov. However, 1)BH3 THF,
2)H2O2 and OH-
will put OH antimarkovnikov.
Hope this helps.

Thanks alot.
I thought ROOR makes it anti-mark no matter what..
Why for Cl is different though?

 

[Doa110]

2. http://en.wikipedia.org/wiki/Electrophilic_aromatic_substitution

Thanks.

 

[heatwheat]

Ok, Markovnikov rule- H goes to the Carbon with the most H`s. You use Markovnikov rule when you are in acid. Acid creates carbocations. For example alkenes with H2SO4, HCl, HI, HBr - react markovnikov.
Antimarkovnikov- you put H to the carbon with the least number of Hydrogens. HBr and ROOR puts Br antimarkovnikov. However, this only works with HBr. HCl and ROOR will still put Cl markovnikov. ALso, H2SO4 and water puts OH markovnikov. However, 1)BH3 THF,
2)H2O2 and OH-
will put OH antimarkovnikov.
Hope this helps.

👍 Know this cold.