I'm pseudonymous. I wear these shades
?O^O? so people won't see how incognito I am.
I had 100 g benzal chloride on hand. I put it in a 1000 ml RB flask, with 500 ml water and 120 g Ca(OH)2, slaked lime, and refluxed for 4 hours, then steam distilled the benzaldehyde. It proves out one of the assertions made in this thread; unfortunately, things happened in the run to make yield suffer, and the the initial oil separation from underneath the water layer amounted to only 22.9 g of benzaldehyde. Well, it doesn't seem enough to go on to the next stage of what I wanted to prove, under my working conditions, so it needs to bee supplemented. Benzaldehyde can also be made by the MnO2 / H2SO4 oxidation of benzyl chloride or toluene itself, and of course by partial oxidation of benzyl alcohol. Benzal chloride, topic of this thread, is the old industrial standard predecessor of benzaldehyde, which is available from benzal chloride by hydrolysis either acid or basic.
Instead of the direct chlorination of toluene, my benzal chloride was brewed in a glass coffeepot, with "saran" stretched over the top to provide refluxing, or let's say retard evaporation of toluene, in a mix of 1:1.66 toluene to calcium hypochlorite by mass. (This was after US 1280612
Post 36700
(CHEM_GUY: "Re: benzyl chloride from hypochlorite salts", Chemistry Discourse) which tells how to make benzyl chloride in a coffeepot outdoors, with a 1:1 ratio of toluene to Ca hypochlorite.) The rxn calls for close temperature control, so use your hotplate. Preferred temperature for the patentee was just over 100°, but for us 90° is better, and our coffeepot run lasts several hours, instead of just an hour. Do not let the toluene reach its actual boiling point, or you have got a thermal runaway, bad smoke, might break glass or give other problems. Allow a moderately vigorous reaction, approximately 75° climbing to 95°. For benzyl chloride it produces just under the 30% conversion of toluene claimed in the patent. Increase the proportion of pool shock tablets to toluene for a benzal chloride run, and there is a higher conversion, but you have toluene and all three chlorinated derivatives for later fractionation.
Now let's pay a little closer attention to what benzaldehyde can do for us: prepare for a surprise. Benzaldehyde condensed with acetaldehyde gives cinnamaldehyde. But that ain't the point. The point: Benzaldehyde chlorinated gives benzoyl chloride. Is that ticking sound coming from inside your head?
Say we need something dry, say this is acetic anhydride. Dick's Practical Receipts (1872)
Post 302737 (missing)
(bocuse: "Nice Old Acetic Anhydride Synth", Chemistry Discourse) suggests reacting benzoyl chloride with dry (fused, powdered) sodium acetate to enable distilling off acetic anhydride. We have a door open here. This discussion continues in
Post 304734 (missing)
(SideArm: "Why Benzoyl Chloride", Chemistry Discourse).
