Did my teacher specialist about sulfur compounds made an error in part of Ramberg-Bäcklund rearragement mechanism?

I have a lot of troubles with what I circled in red with the big question mark near. I am not speaking about stereochemistry but about conservation of number of hydrogen atoms, and also there is actually no reason for the electrons on the carbon near $R\_1$ to attack the other carbon. In my lesson, the teacher didn't show how the extra hydrogen was removed.


Can you explain what my teacher didn't show or forgot to include? 


[![Ramberg-Bäcklund rearrangement](https://i.stack.imgur.com/gPeWf.jpg)](https://i.stack.imgur.com/gPeWf.jpg)


Thank you in advance!




As discussed above, the pathway shown on the left is incorrect because it essentially shows insertion into a $\ce{C-H}$ bond by an anion with loss of $\ce{X^-}$, which is not the easiest path for this reaction to take by a long shot.


The actual mechanism for this reaction is as shown below.


1. First, the non-halogenated alpha-carbon is deprotonated.
2. The carbanion formed arranges itself such that the it can attack the halogenated carbon and in such a way that the two R-groups are *cis* to each other.
3. Attack occurs, with loss of $\ce{X^-}$. Product is *cis*.
4. In water, due to lack of solubility, decomposition is faster than redeprotonation and the (Z)-alkene forms.
5. In organic solvent, base deprotonates an alpha-carbon, which can then scramble.
6. The main reprotonation product is the *trans* product.
7. The *trans* product decomposes, and the (E)-alkene is the major product.


[![Ramberg-Bäcklund mechanism](https://i.stack.imgur.com/dn0Ri.png)](https://i.stack.imgur.com/dn0Ri.png)


A few notes:


* The red path makes almost completely (Z) product. The blue path makes a mix of the two with the (E) product as the main product.
* Purple star: the reason the anion attacks to form the *cis* ring is unknown, but there are several theories, apparently.
* Green stars: cheletropic ring decomposition is symmetry forbidden, so this is theorized to be a two-step decomposition through either diradical bond fissions or a dipolar mechanism.


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