[Rutherford]

What pairs are the diastereoisomers? What property makes those pairs to be distinguishable in fraction destillation process?

[sjb]

What pairs are the diastereoisomers? What property makes those pairs to be distinguishable in fraction destillation process?

See e.g. http://en.wikipedia.org/w/index.php?title=Diastereomer&oldid=491533938 or similar

[discodermolide]

What pairs are the diastereoisomers? What property makes those pairs to be distinguishable in fraction destillation process?

(R)(R)/(S)(S) are one pair
(R)(S)/(S)(R) are the other.

They have different physical properties, BPt, MPt., NMR, etc.
Have a look here.
http://www.ch.ic.ac.uk/local/organic/tutorial/ACS4.pdf

[Rutherford]

sjb I read that link before and it didn't tell anything about the physical properties of diastereoisomers.
discodermolide, your link, sadly confused me a bit, because on the scheme  (R)(R) is a diastereoisomer with both (R)(S) and (S)(R), but I saw that there were same groups attached to both chiral centers, the I understood it.
So the diastereoisomers have different properties, and there will be different fractions, but the fractions are not optically active because they are racemates.
Thanks very much for helping me with this, I understand a lot more of diastereoisomers and enantiomers.

[discodermolide]

sjb I read that link before and it didn't tell anything about the physical properties of diastereoisomers.
discodermolide, your link, sadly confused me a bit, because on the scheme  (R)(R) is a diastereoisomer with both (R)(S) and (S)(R), but I saw that there were same groups attached to both chiral centers, the I understood it.
So the diastereoisomers have different properties, and there will be different fractions, but the fractions are not optically active because they are racemates.
Thanks very much for helping me with this, I understand a lot more of diastereoisomers and enantiomers.

Good, my pleasure.

[sjb]

sjb I read that link before and it didn't tell anything about the physical properties of diastereoisomers.

OK, no problem, it may not mention your compound specifically, but there are snippets in the text, e.g.

The names are derived from the diastereomeric aldoses erythrose (a syrup) and threose (melting point 126 °C).

or

..two diastereomers will not have identical chemical properties.

Glad it's all sorted now anyway