Some bees seems to have failed miserably trying to follow some of my writeups. I don´t know which reactions has failed or who theese bees are since none of them has asked me directly. The issue seems to be the
catalyst. It also seems like I am the one to blame for this since I haven´t described which catalyst I have used. For this I am sorry!
The catalysts I use, 5% Pd/C in 99% of the cases, is
never homemade. I tried to make my own 5% Pt/C and 5% Pd/C on two occasions, and failed terribly. Then I bought the catalyst from Sigma-Aldrich and it worked great. I used this supply-house bought catalyst for about one year until I relized I was spending a fortune buying catalysts from them. Actually one is spending a fortune buying anything from them. So I decided to buy the catalysts from the manufacutrer instead. The price I payed to buy 100 g 5% Pd/C from Si-Al got me 1 kg top quality 5% Pd/C from the manufacturer.
I know most bees will never be able to buy from the manufacturers, and this is a pity since this is the secret to get really good yields IMHO.
Which catalysts am I using then?
From Johnson Matthey:
Type 38H and 87L 5% Pd/C, equally good for most CTH reductions.
Type 325 5% Pd/Al2O3, very good for low-pressure hydrogenation of nitropropenes to ketoximes.
Type 18 5% Pt/C, very good for schiff´s base reductions.
Degussa:
E 105 O/W 5% Pd/C, very good for most types of CTH reductions
Raney nickel can be made if one can get the Ni/Al alloy
Post 361199
(Barium: "Preparation of Raney-nickel", Methods Discourse).
Remember that the activity of
all catalysts decreases with time. Some faster than others. If you have made the 5% Pd/C yourself, which seems to give a catalyst of very low activity for most bees, and store it for months and months there is no wonder why the yields are crappy.
Catalytic hydrogenation freak