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- Solutions 63

Consider each pair of compounds below and determine whether the pair represent the same compound, constitutional isomers, or different compounds that are not isomeric at all:

Alright guys. So, for this question, we have these two different compounds, one has a double bond and one has a triple bond and they're both five carbons in total, so we have 1, 2, 3, 4, 5 double bond 1, 2, 3, 4, 5, okay? So, again, let's just count our carbons here we have 1, 2, 3, 4, 5 carbons on one, 1, 2, 3, 4, 5, 5 carbons on the other, okay? So they're both C5 and this one's C5, this one is C5 then we can go about this two different ways, I'm going to tell you guys the shortcut first. Notice that we have an alkene and alkyne. Now, based on the number of carbons they have, we can actually predict the number of hydrogens that they have, because remember that for alkenes, right? Which is what this is, we're going to see that C to the N is H to the 2N, the hydrogens are going to be double, so this should be C5H10 and if you count the hydrogens you'll see we have 10 hydrogen's. Now, for alkynes right? The triple bond, what is the general form of that we can assume for these CN, right? H2n as well but now it's going to be minus 2, right? For alkyne, so we can predict that this formula is going to be C5H8, count the hydrogens you'll see that C5H8, we have three coming off here to here to here, one and two. So, three, two, two, that's seven eight, nine and ten, okay? So we can just say 1 and then 2 here, with 10 hydrogens again 3, 2, 2 and how many here, none and 1 here, so we have in total 1, 2, 3, 4, 5, 6, 7 and 8, okay? So, using that shortcut by knowing that the alkene form is going to have to double the number of hydrogen's than carbons and alkynes are going to have double the amount of hydrogens minus 2, okay? So, as you can see their formulas are different from each other, they're molecular formulas, what does that mean? you think they're going to be the same? No, well, constitutional isomers also said they have the same formula but different connectivity, here guys, they have different molecular formula, so we're going to say that they're different compounds. Alright guys, so hopefully this makes sense and let me know if you have any questions.