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As you have mentioned, the basic Fischer operations are: Vertical positions are below the plane of paper and horizontal positions are Above the plane of paper, thus you have already remember that when working with Fischer projection. What you have to remember about chiral compounds are: If you switch two groups, you get the epimer and if you switch two other ...
answered Jun 17 '21 at 20:02
Mathew Mahindaratne
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There are two possible eliminations that can happen (see the image below)
As you can see, we then have two final products depending upon which $\ce{H}$ is eliminated. From the image 1a is cis and 2a is trans. Now, how do we decide which one is the major product?
This can be based on looking at the stability of the transition state. This means we have to ...
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This was going to be a comment but it got too long.
TL;DR: - This is not an answer, rather a justification for why the question is (probably) wrong.
This paper (linked by @Rishi) gives us experimental evidence that under action of concentrated $\ce{H2SO4}$ hydrogens are exchanged from paraffins in the following fashion:
$$
\begin{align}
\ce{(CH3)2CHCH3 + ...
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$\ce{C-H}$ bond and $\ce{C-D}$ bonds are not the same in energy. $\ce{C-D}$ bond is stronger. So breaking $\ce{C-D}$ bond is more difficult and slower than breaking $\ce{C-H}$ bond.
I hope you know the mechanisms of $\mathrm{E1}$ and $\mathrm{E2}$ reactions. In $\mathrm{E1}$ reaction, a carbocation is formed first, which is the rate-determining step (rds). ...
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Cope elimination is a pericyclic reaction that always prefers syn-elimination. Due to hydroxylamine being a poor leaving group, the reactions often tend to prefer hofmann products.
However the reason for preference towards hofmann products is the stability of carbanion formed due to less $\ce{\alpha-H}$ and consequently less destabilization by +H effect. (...
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Dehalogenation of vicinal dihalides can occur through the E2 mechanism. After some digging, I found this article from 1955. The full text is behind a paywall for me, so I cannot cite the specific rate constants, but the general findings are that trans-1,2-dihalocylohexanes undergo iodide-mediated dehalogenation more rapidly than the cis-stereoisomer.
These ...
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Notice, that the first compound (A)can show tautomerism, after drawing the enol form we find that the carbocation lies at the allylic position, which means that it is stabilised through resonance forms, hence the compound A has highest rate of reaction.
Hope it helps.
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Thanks to @Mithoron, @Waylander and @M.L for your insightful comments! Willstatter's synthesis is described in greater detail on synarchive, as shared by M.L. Indeed, as Mithoron pointed out, 1,4-addition to the diene formed after Hofmann elimination occurs. Subsequent elimination with the base quinoline yields the triene, as depicted below.
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I believe the mechanism should be somewhat like this (after the formation of carbocation) -
It would account for the product shown, but I am not sure if it's correct. I feel it's more favourable for a dehydration to occur with the hydrogen from the ring itself (shown on the dash at the top) to form this -
This double bond is conjugated and more substituted,...
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The concept here is that after the formation of the alkene (propene, in this case), it is much more easier to abstract the vinylic hydrogen as compared to the allylic hydrogen and thus preferring the formation of alkyne (propyne, in this case) over the formation of a diene (prop-1,2-diene, in this case).
Remember, $\mathrm pK\mathrm a$ of vinylic systems is ...
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