Week 7+8 question 18

[606012329]

I'm confused as to how to determine the different structures of H2CCH2, H2CCCH2, and H2CCCCH2. If someone has a picture they could upload of the different structures, that would be really helpful.

[Hayden Zhao 3C]

I unfortunately don't know how to upload pictures, but I'll try my best to describe them.
H2CCH2:
The two C are in the middle connected by a double bond; two H atoms are attached to each C.
H2CCCH2:
The three C are in the middle connected by two double bonds; two H atoms are attached to each C on the two sides.
H2CCCCH2:
The four C are in the middle connected by three double bonds; two H atoms are attached to each C on the two sides.

Since H atoms never go in the middle of a molecule, you just connect the C chain and add H to the C atoms on the sides. You'll have to calculate oxidation numbers and formal charges, which will tell you that the C atoms in the chain are connected through double bonds, so the H can only go to the sides.