[acegsm]

Hello, I am having trouble with several mechanisms on the program ACE Organic. 

Problem One:



This is what I tried to do:



The error read: The electron-flow arrows in the highlighted step do not lead to any of the products drawn in the subsequent step. See the products ACE has calculated from the electron-flow arrows in the highlighted stage.


Second One I had trouble with:



I put:



Error read: The electron-flow arrows in the highlighted step do not lead to any of the products drawn in the subsequent step. See the products ACE has calculated from the electron-flow arrows in the highlighted stage.

[nj_bartel]

both your mechanisms look good to me.  I'd ask your professor.

[acegsm]

Thanks.  That is strange.  I also have two other questions I thought were right, should I ask about these:



My answer:



Error:  Your mechanism lacks one of the given reagents. Both H2SO4 and H2O are required for this reaction to occur. The alkene starting material should also be present.



My answer:


Error: If the OH group weren't present in the substrate, this answer would be correct, but the OH group participates in the reaction.

[jj74]

the second reaction looks good to me. For the first, check the second step, I think that the first six atoms ring you draw is wrong; I find helpful, in these ring expansion reaction, to number all the atoms in the substrate to see where the are in the product

[KritikalMass]

I think it is not a problem with your mechanism but rather a problem with the software thinking you're arrowing pushing to the wrong parts of molecules.

In the first one is there any way to draw the arrow from the DB so that it is almost on top of the H in the HBr?

In the second one is it possible to draw the arrow from the DB so that it is almost on top of the H in the HCl? The way it is drawn now it looks like the DB is attacking the hydroxy group.

[Arctic-Nation]

jj74 is correct, there's an error in the mechanism of the first reaction.

For the third reaction, I'm not really sure what you're trying to accomplish by reacting the alkene with water first and then with methanol. A direct reaction with methanol seems much simpler.

The fourth reaction lacks the bromination reagent, but assuming that it's molecular bromine you'll never get a single stereoisomer. There's no chirality in the starting material, so you'll always end up with a racemic mixture. However, I'm not sure if the presence of the hydroxy group really has an influence on the reaction pathway.

[nj_bartel]

Oops, missed it in the first mechanism.  Agree with the above.

[jj74]

maybe for the third reaction you should specify the reaction of H2SO4 with water to give hydronium, which is the active species present that protonates the alkene:

H₂SO₄ + H₂O    H₃O⁺ + HSO₄^-
H₃O⁺ + CH₃CH₂CH=CH₂   CH₃CH₂CH⁺-CH₃
CH₃CH₂CH⁺-CH₃ + CH₃OH  CH₃CH₂CH(CH₃)O⁺HCH₃  deprotonation : product

[Dan]

However, I'm not sure if the presence of the hydroxy group really has an influence on the reaction pathway.

Once you form the bromonium I think the presence of the hydroxyl is very important...

[jj74]

yes indeed, in the 4th reaction, after the bromonium ion is formed, there's another nucleophile present in the reaction medium other than Br^- that opens the cyclic ion and the product is a ring, is it right ?