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Regarding user55119's comment about methylamine: about the train scene, they didn't steal methylamine per se from that train, they stole aqueous methylamine, i.e. a 40% methylamine solution in water. This solution has a different density than water, thus explaining the need to compensate with a slightly different volume of water, and explaining why WW talks ...

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@Ivan Neretin, in his comment soon after your post, essentially solved the problem for you. In a comment I subsequently tried to set you in the right direction. Now that the ten structures have been posted in an answer and you have had time to think about a solution, here is the methodology to get the correct answer if you haven't solved it on your own.All ...

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The given compound 2,3,5,6-tetrachloroheptane has 10 isomers. These have been shown below. The compound 2,3,5,6-tetrachlorooctane in the link does not have a meso compound. The terminal groups, methyl and ethyl are different and therefore meso form is not possible. The possible combinations have been given below, which are 16.

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I am quoting from IUPAC GOLD book$^1$ . Meso-compound : A term for the achiral member(s) of a set of diastereoisomers which also includes one or more chiral members. For example: There is a plane of symmetry in the examples given in IUPAC GOLD book (shown in colour) . Molecule $\ce{3}$ also has a plane of symmetry as shown in the figure below. This ...

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Almost everything that needs to be said has been said. But I do have a few comments about configurations. In enantiomeric, trans-dibromides 1 and 2, the methyl groups are chirotopic and non-stereogenic. Inversion of the stereochemistry of the methyl group in either 1 or 2 returns the same structure, respectively. Thus, there is no designation for ...

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Nice pictures and analysis! There are four different stereoisomers: one pair of enantiomers (the trans structures) and two achiral isomers (the cis structures). In a mixture of all four, there will be 3 sets of boiling points, peaks in chromatographic separation (with achiral columns), etc. 1,2-dibromo-4-methylcyclopentane has two chiral carbon atoms, ...

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