Chem questions

[mag7ical]

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Here's a GC & Orgo question. Can anyone explain the solutions? Thanks!

1. Iron reacts with element X to form the compounds FeX and Fe3X2. When copper reacts with element X, the expected compound(s) should be:
A. Cu3X and Cu3X2.

2. What forms when H3CC≡CH reacts with a) NaNH2/NH3 then b) CH3Br?
A. H3CC≡CH3

 

[mashinka]

alright so for A, we know that iron is ferric and ferrous meaning that it has a 2+ and a 3+ positive charge associated with it. Therefore, for FeX we can assume that X has a 3- charge and Fe(III). This works for Fe3X2 as well when we consider Fe(II)

Cu, also has can be (I) or (II). So, knowing that X is 3-, if we assume Cu(I) then we would need 3 equivalents of Cu so it can have a 3+ charge and thus pair with X.

For Cu(II), we would need 3 equivalents to go with 2 equivalents of X. That way, we have a 6+ charge pairing with a 6- charge.

For the second question.....the answer seems totally wrong. The second Carbon has 6 bonds attached to it, which is definitely too many. Check your answer key again, i think it should be H3CC≡CCH3, not H3CC≡CH3
My guess is that the Na+NH2/NH3 deprotonates H3CC≡CH, making H3CC≡C-, which is a nucleophile. For CH3Br, the Br is a great leaving group. So the nucleophilic alkyne can now perform an SN2 displacement on the CH3Br, making H3CC≡CCH3

 

[UndergradGuy7]

2. What forms when H3CC≡CH reacts with a) NaNH2/NH3 then b) CH3Br?
A. H3CC≡CH3

NaNH2/NH3 is a base. The H on the triple bond carbon is acidic. So it makes H3CC≡C- then attacks the CH3Br and becomes H3CC≡C-CH3.

 

[mag7ical]

Thanks!