[trinhn812]

http://i45.photobucket.com/albums/f84/azncrombie/steromers.png

I thought it was:
i. same
ii. diastereomers
iii.enatiomers
iv.diastereomers

But it said i was wrong. Any ideas?

[azmanam]

III and IV are wrong

BIG HINT: redraw one of them so it's in the same orientation as the other and looks as much as the other as possible, then do your analysis.

[Fridushka]

Aren't in the (i) enantiomers? or enantiomers and same..are the same  ?!

[azmanam]

they are the same molecule.... there's a special term for this case (and probably a better answer, imho).

[jj74]

iv: check the configuration (R/S) of the two asymmetric carbons in the two structures

[trinhn812]

Oh they third one fooled me. It's the same one, correct?

and the last structure, is priority OH>That long R group>CH2CH3?

For question 4, I got R and R for figure A. and R and S for figure B.

[trinhn812]

I think I'm getting more confused. Isn't ii. the same compound?

[Fridushka]

yeah i think so.., in my openion (i) is enantiomers
                                          (ii) is the same
but I'm not sure of the (iii) & (iv)..

[azmanam]

i. and iii. are the same compound (although if you put 'same' you'll get the answer wrong.  there's a better descriptor that you need to use to get the answer right).

ii. and iv. are NOT the same.  You were right the first time that ii. is diastereomers.  for iv. (well, for all of them really) you should redraw them so they're at least the same projection (i.e. both line angle drawings (preferred) or both Fischer projections or whatever).  then rotate the various bonds until as many of the in-the-plane bonds in one molecule are in-the-plane in the second molecule (that is, get the two to look as much alike as possible) then do R/S  analysis on each of the chiral centers (if there are any) and evaluate.

See here for more rotation/redrawing hints:
http://www.chemicalforums.com/index.php?topic=33818.0
http://www.chemicalforums.com/index.php?topic=28328.0
http://www.chemicalforums.com/index.php?topic=32203.0

[jj74]

Oh they third one fooled me. It's the same one, correct?

and the last structure, is priority OH>That long R group>CH2CH3?

For question 4, I got R and R for figure A. and R and S for figure B.

check the priorities, I think everyone has his better way of visualize molecules in three dimensions; I usually transform them in an eclipsed sawhorse projection  and then in a Fischer projection; then I find easy give the descriptors to the asymmetric carbons