[Borek]

An olefin reacting with Br₂ yields a substance containing 69.50% bromine and a single chiral carbon. Name the olefin.

[fledarmus]

I'll try this one! How about "George"? Or maybe "Bob"? Or "Sue"...

[discodermolide]

I think I know the answer, but will not spoil it for others.
But following Fledarmus's lead I will call it Fred as in Flintstone.

[Borek]

Nice try, but I was thinking about more systematic approach 

[discodermolide]

Well I used my drawing tools, which give elemental analysis. Going through the parameters you give it spat out Fred Flintstone.
I stlll don't want to spoil it for others. You must insist that I provide an answer. But let's wait a bit

[CrazyAssasin]

I'm not certain about the answer, but I think it's should be 2-metil-1-butene

[Rutherford]

I don't understand how only one olefin could be the answer. I got two actually.

[CrazyAssasin]

Could you name them, because I can find only one.

[Rutherford]

Yours, and 1-pentene, which has a chiral C atom too (H, Br, CH₂Br and C₃H₇ are bonded to him).

[CrazyAssasin]

Yes you're right, I didn't think about this one.

[fledarmus]

What about 2-methyl-2-butene?

[Rutherford]

Yes, that one has a chiral C, too.

[Schrödinger]

Yeah, so don't we have 3 possibilities? Just consolidating : pent-2-ene, 2-methylbut-1-ene and 2-methylbut-2-ene.

[Borek]

You should already know if the question I posted contains word "chirality", something must be wrong 

More seriously, question was intentionally lousy. To be honest I didn't even know how lousy it is - that is, I knew of two possible reasons why the answer is not unique (BTW: one was not yet mentioned in the thread, although I was contacted by PM by fledarmus), could be there are even more problems with the question. But I wanted to stir a discussion and I know from experience best way to catch your attention is to post some kind of nonsense 

I wanted to ask you about Problem of the Week - do you think it makes sense to continue (I do plan to), do you have any ideas about how to make it more interesting, do you know questions that you think will fit, or perhaps you just have an idea that you think could be made into an interesting question with some work?

[Rutherford]

" do you think it makes sense to continue"
Continue please, there were many interesting problems.
These are my favorites till now:
http://www.chemicalforums.com/index.php?topic=59349.0 interesting because of the story
http://www.chemicalforums.com/index.php?topic=57924.0 interesting because of using more maths (quadratic inequality)
http://www.chemicalforums.com/index.php?topic=58982.0 one really really nice problem. Would like to see similar.
I didn't like some of the inorganic guessing tasks (this is only my modest opinion of course), and I would like to see organic more (would be nice to have some problem of the week in the organic section that is for students-not professionals. I started to learn it 3 months ago and I found it very interesting, but never mind).