Large-Scale Methamphetamine Manufacture

4.0 Manufacture of 1-phenyl-2-propanone

The manufacture of P2P utilizing benzaldehyde and nitroethane is described. We will be using a two-stage procedure involving the Cope modification of the Knoevengel reaction and an iron-acid reduction procedure. The chemistry of this procedure has been described by Uncle Fester in his Secrets of Methamphetamine Manufacture, 3rd ed., thus we will concentrate on scaling up the reaction to the point where it can be used for very high-volume manufacture.

4.1 Equipment

The following equipment will be required.

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  A rigid-base heating mantle with dual-element controls that holds a 22-liter round-bottom triple-neck.
  
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  A 22-liter, 3-neck, round-bottom reaction flask
  
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  A 45/50 to 24/40 glass fitting adapter
  
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  A Dean-Stark trap
  
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  Two 30cm West condensers
  
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  Several 5-liter and 20-liter plastic buckets
  
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  Fabricated equipment described below
  

4.2 Chemicals

Benzaldehyde
This is our basic starting material. One mole of benzaldehyde weighs close to 100g and has a density close to 1g/ml. Since we will be performing 25-mole reactions, we will use 2500ml of benzaldehyde per reaction. All other reactant quantities are derived from this figure. Purchase the chlorine-free type if available, but the standard product works fine. Store in a cool, dark place. Benzaldehyde will auto-oxidize somewhat over time, but is nothing to get excited about-this stuff will keep. The oxidation product is benzoic acid, which takes the form of well-defined white crystals at the bottom of the container. Try not to get any of the crystals into the reaction. They won't kill it, but will reduce the yield. Benzaldehyde has a strong odor of marzipan. It can be vacuum-distilled in order to clean it up, but has a tendency to bump vigorously at vacuum levels that are high. Benzaldehyde has been relatively easy to obtain until recently.
Nitroethane (EtNO₂)
This is the material we will react with the benzaldehyde molecule in order to produce 1-phenyl-2-nitropropene. It supplies the carbon sidechain and nitro group that are required to produce the nitrostyrene. EtNO2 is a clear, pleasant- smelling liquid which boils at 114-115°C, has a molecular weight of 75.07g/mol, and a relative density of 1.05. It distills nicely without vacuum. Since we will be providing a 5% excess of nitroethane in order to ensure there are enough molecules available to combine with the benzaldehyde, we will require 26.25 moles of nitroethane((26.25mol x 75.07g/mol)/1.05), or 1,875ml for each batch. One can use the industrial grade nitroethane, but it must be washed and distilled before using. To clean it up, pour about 3000ml of nitroethane into a 4000ml separatory funnel, add 500ml of distilled water, shake thoroughly, allow the water to separate to the top over a 24-hour period, then drain the nitroethane and distill it, discarding anything that comes over below 110°C. It is important that the nitroethane be clean. One should be aware that nitroethane has become a high-suspicion product because it sounds much like nitromethane, which is the booster that was added to the Oklahoma City bomb. Do not confuse the two.
n-butylamine (n-BuNH₂)
This is our catalyst. Do not use "sec-" or "tert-" butylamine, as they will not work(the "n-" means "straight- chain"). In addition, because n-butylamine is a very strong base which reacts with carbon-dioxide in the air and almost anything else it contacts, one must insure that the catalyst is clean. The best way to do this is to distill it. Do this inside a fume cabinet as this stuff is very ugly. Don't breathe it and don't touch it. One must wrap the stopper or cork on the distillation rig in Teflon tape to prevent it from being eaten. The amount of catalyst used in our 25-mole reaction is nominally 20ml/mole, but experience has shown that the actual amount is closer to 23ml/mole, so one should purchase an amount that will provide a volume of 25ml/mole of benzaldehyde. The actual amount must be determined by observation and adjusted accordingly. The use of catalyst that is not pure will result in a drastic reduction in yield.
Ferric Chloride (FeCl₃)
This innocuous chemical is used in our reduction reaction in small quantities as a "steerer", which modifies the reaction equilibrium in the direction we desire. A few kilos of this can do a lot of reactions.
Catalytic Iron Powder (Fe)
Used in the reduction procedure, the iron reacts with hydrochloric acid to produce hydrogen gas. Due to the requirement for good dispersion during the reduction, the use of a fine mesh powder is necessary, either 80 or 100 mesh. A coarser 60 mesh powder can be used, but may result in some problems if the stirring system is inadequate. The reaction requires 200g of iron powder for every mole of 1-phenyl-2-nitropropene that is reduced. Since we will be performing 20- mole reductions, each reduction will require 4000g of iron.
Muriatic acid (HCl)
This is simply dilute hydrochloric acid, usually about 28-32% as compared with 37% HCl. It works just fine, however, and has the advantage of being available at almost any hardware store. A volume of 750ml of 37% HCl is required for every mole of 1-phenyl-2-nitropropene that is reduced, resulting in 15 liters of acid required for every 20-mole reduction. It has been this writer's experience that the more dilute muriatic acid performs just as well as the stronger stuff in the same volume.
Methanol (MeOH)
This is used as a solvent when processing the yellow nitropropene crystals. Purchase methanol which has not been diluted with water-some of it is only 60% methanol. Keep it in the deep freeze.
Toluene
This is our solvent for the Knoevengel reaction. It is available in every paint store, although many companies are relabeling their solvents with house names so the narcs don't hassle them. Use the "UN" number, which must be on every container, to identify the product. Or just ask. Most paint store employees don't know the difference between toluene and neoprene and will happily tell you anything you want. Our Knoevengel reaction requires 200ml of toluene for every mole of benzaldehyde, or 5000ml for every reaction.