[Kayla]

I need help on 15-20. I cant figure out what reagents to use. Please help thanks

[sjb]

Do you know how to get there if there was no labelling introduced in those reactions?

[Schrödinger]

Seeing that you've solved most of the other ones, this has got to help you :

15 and 16 : Anti-addition of OD instead of OH.

[Zainb]

10 the ozonolysis of olefins to ozonides and the subsequent conversion to aldehydes  in reductive workup conditions
11 and 14 is oxidation of hydroxy group with Dess-Martin periodinane.

[Borek]

Really no need to cry in blue.

[bromidewind]

17. Use OsO₄ and D₂O₂ -> Syn addition of OD
      Or you can use cold, dilute KMnO₄, followed with ^-OD, D₂O.
15, 16. Use a peroxyacid (peroxyacetic acid, MCBPA) to form an epoxide ring, then use D₃O to open the ring and get anti-addition of OD
18. Pd/BaSO₄, quinoline
Not sure about 19
20. 2 D₂ and a metal catalyst like Pt, Pd, or Raney nickel