Double checking organic chem mechanisms

In summary, the OH added to the C bonded with the R because it was the most substituted carbon in the alkenes.
  • #1
future_vet
169
0
Hello,

I need to make sure I understand some of the reactions correctly... For example:

CH2OHCH3 in H+ will give us CH2=CH2. I would think that here the H+ bonded with the OH resulting in H2O (a leaving group), but I am not sure what happens to the other leaving H.

In RC≡CR' in Na/NH3, we get RCH=CHR' in an anti addition. Where did the 2 H come from? The NH3?

RCH=CH2 in H3O+ gives RCHOHCH3. Did the OH and H come from the H3O+? Do we then have one last H that does not bond with the molecule? And did the OH add to the C bonded with the R because it is the most substituted carbon?

In RCH=CH2 in (1) Hg(OAc)2/H2O and (2) NaBH4, NaOH, we get RCHOHCH3. Where did the OH and H come from? Did the OH add to the C bonded with the R because it is the most substituted carbon?

In RCH=CH2 in (1) BH3/THF and (2) H2O2/OH- we get RCH2CH2OH. Did the OH add to the C because it was the least substituted? Also, is the mechanism the following: first, Br (from BH3) bonds with the least subst. carbon, and H also from BH3 adds to the other C, thus breaking the double bond. Then in step (2) Br is replaced by OH, from OH-.

And finally:
a) ROH + SOCl2 -> RCl
and
b) ROH + TsCl ---(base)--> ROTs

These 2 reactions confuse me. I thought that in a) the H would bond with a Cl giving HCl + RSOCl. Why does it give RCl?
However in b) what I thought would happen in a) does take place. H and Cl bond, resulting in ROTs. Why?

Thank you so much for your help, I hope I was clear enough!
 
Physics news on Phys.org
  • #2
future_vet said:
CH2OHCH3 in H+ will give us CH2=CH2. I would think that here the H+ bonded with the OH resulting in H2O (a leaving group), but I am not sure what happens to the other leaving H.
The acid is H+A-. The other H atom (through a carbocation mechanism) goes away with the conjugate base, A-
 
  • #3
Thanks!
 
  • #4
future_vet said:
In RC≡CR' in Na/NH3, we get RCH=CHR' in an anti addition. Where did the 2 H come from? The NH3?
Yes, one H-atom from each NH3.

RCH=CH2 in H3O+ gives RCHOHCH3. Did the OH and H come from the H3O+? Do we then have one last H that does not bond with the molecule? And did the OH add to the C bonded with the R because it is the most substituted carbon?
Yes, yes and yes. Look up the mechanism for electrophilic addition to alkenes through carbocation formation on the most substituted carbon.
 
  • #5
Thank you so much, you're so helpful!
We rarely get the mechanisms in class, as we are told we have to do a lot of memorization. But I found that understanding the mechanism allows me to remember the reactions for the rest of the semester, instead of relying on memorization.
 
  • #6
future_vet said:
In RCH=CH2 in (1) Hg(OAc)2/H2O and (2) NaBH4, NaOH, we get RCHOHCH3. Where did the OH and H come from? Did the OH add to the C bonded with the R because it is the most substituted carbon?

In RCH=CH2 in (1) BH3/THF and (2) H2O2/OH- we get RCH2CH2OH. Did the OH add to the C because it was the least substituted? Also, is the mechanism the following: first, Br (from BH3) bonds with the least subst. carbon, and H also from BH3 adds to the other C, thus breaking the double bond. Then in step (2) Br is replaced by OH, from OH-.
You will find these mechanisms in any standard O Chem text. In Morrisson & Boyd (6th Ed.), this is in Ch 9: Reactions of Alkenes.
 

1. What is the purpose of double checking organic chem mechanisms?

Double checking organic chem mechanisms is important because it helps ensure the accuracy and validity of the proposed reaction pathway. It allows for identification and correction of any errors or discrepancies in the mechanism, which can ultimately lead to more reliable and reproducible results.

2. How do you double check an organic chem mechanism?

Double checking an organic chem mechanism involves carefully examining each step in the proposed pathway and verifying that it follows the principles of organic chemistry, such as electron movement and stability of intermediates. This can also include conducting additional experiments or simulations to support the proposed mechanism.

3. What are some common mistakes in organic chem mechanisms that should be double checked?

Some common mistakes in organic chem mechanisms include incorrect electron movement, incorrect stereochemistry, and missing or misinterpreted intermediates. It is important to carefully review each step and ensure that it aligns with established organic chemistry principles.

4. Why is double checking organic chem mechanisms important in research and experimentation?

In research and experimentation, double checking organic chem mechanisms is crucial for ensuring the validity of the results. A small error in the mechanism can lead to incorrect conclusions and hinder the progress of the research. Double checking mechanisms can also help identify new or unexpected reaction pathways, leading to further discoveries.

5. How can one improve their skills in double checking organic chem mechanisms?

Improving skills in double checking organic chem mechanisms involves gaining a thorough understanding of organic chemistry principles and regularly practicing mechanism analysis. It can also be helpful to seek feedback and guidance from experienced researchers or instructors. Additionally, staying updated on new developments in the field can improve one's ability to critically evaluate and double check mechanisms.

Similar threads

  • Biology and Chemistry Homework Help
Replies
6
Views
2K
  • Biology and Chemistry Homework Help
Replies
1
Views
2K
  • Biology and Chemistry Homework Help
Replies
2
Views
6K
Replies
17
Views
2K
  • Biology and Chemistry Homework Help
Replies
1
Views
5K
  • Biology and Chemistry Homework Help
Replies
2
Views
2K
  • Biology and Chemistry Homework Help
Replies
2
Views
5K
  • Biology and Chemistry Homework Help
Replies
4
Views
7K
Replies
8
Views
4K
  • Biology and Chemistry Homework Help
Replies
2
Views
10K
Back
Top