PHENYLACETONE FROM B-KETO ESTERS
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In this chapter, I will cover two separate but similar methods of
making phenylacetone. Neither of them is actually suitable for
industrial-scale production, but they have the advantage of not using
phenylacetic acid. This allows an underground chemist to diversify the
chemicals used, and enables him to defeat a blockade on his phenylacetic
acid supply. Neither of these reactions is foolproof; both require a
certain amount of laboratory skill. The chemicals must be weighed and
measured fairly exactly. This is unlike the method described in Chapter 3,
where anything within a ballpark range will work. These methods require a
reliable scale.
Both of these reactions use sodium metal, which is some nasty stuff. It
reacts violently with water to produce sodium hydroxide and hydrogen. It
will also react with air. The chemist never touches it intentionally; if he
does touch it, he washes it off with warm water. Sodium metal comes in a
can, covered with a bath of petroleum distillate. This is to protect it
from water and air. As long as it stays covered, it causes the chemist no
problems.
In this reaction, sodium metal is reacted with absolute alcohol to make
sodium ethoxide (NaOCH2CH3). Ethyl acetoacetate and bromobenzene are then
added to this to produce a beta keto ester. Reaction with acid then
produces phenylacetone.
A side reaction which sometimes becomes a problem is bromobenzene
reacting with beta keto ester to produce di-phenylacetone. This can be
controlled by not using too much bromobenzene, adding it slowly and
stirring it well.
Figure 12 shows the glassware used. The glassware must be very dry, so
it is dried out in the oven for an hour or so. If the sep funnel has a
plastic valve, the valve is taken out before the sep funnel is put in the
oven. The magnetic stirring bar does not go in the oven either. It is
coated with Teflon, so it does not have any water on it. A magnetic stirrer
is necessary to do this reaction, because good stirring is very important.
An extra claisen adapter is needed for this reaction; one is filled with
broken pieces of glass for use as a fractionating column, the other is kept
as is for use in the Figure 12 apparatus.
To begin, the underground chemist puts a bed of Drierite in the vacuum
adapter as shown in Figure 2a, being sure to plug up the vacuum nipple. The
water lines are attached to the condenser and cold water started flowing
through it. But if it is humid, the water flow is not started until the
glassware is assembled.
The can of sodium is opened. A chunk about the size of a medium egg is
needed. The chemist selects a convenient corner of the block of sodium to
work on. With a clean, sharp knife, he scrapes off any discolored skin
there might be in the area he plans to use. Good clean sodium has a bright
metallic look. He keeps the block under the petroleum as he scrapes the
discolored skin.
Now he must weigh the sodium. A 100 ml beaker is filled halffull of the
petroleum distillate from the can of sodium, or with xylene. He puts it on
the scale and weighs it. He needs 34.5 grams of sodium metal, so with a
clean sharp knife. he cuts off a chunk of sodium, transfers it to the
beaker and weighs it. If it is not quite 34.5 grams, he cuts a little more
sodium and adds it to the beaker. This is done quickly, so that evaporation
of the petroleum does not throw the measurement off. Then another 100 ml
beaker is filled half-full of anhydrous ethyl ether. The sodium metal is
transferred to it with a spoon. The petroleum is poured back in with the
block of sodium and the can sealed up so that it does not evaporate. With a
clean sharp knife, the sodium is cut up into little pieces about 1/2 the
size of a pea.
The sodium is kept under the ether while this is being done. Eye
protection is always worn when working with sodium.
After the sodium is cut up, the magnetic stirring bar is put in the
2000 ml flask. Then the sodium metal pieces are scooped out with a spoon
and put in the 2000 ml flask. The glassware is immediately assembled as
shown in Figure 12. One liter (1000 ml) of absolute ethyl alcohol is
measured out. Absolute alcohol absorbs water out of air, so this is done
rapidly. Here's how. The chemist gets a quart beer bottle, marks on the
outside how full one liter is, and bakes the bottle in the oven to dry it
out. When he takes it out of the oven, he sucks the hot, moist air out of
it with a section of glass tubing. Once it has cooled down, he fills it
with one liter of absolute alcohol and stoppers it to keep it dry. He wants
to get the alcohol in with the sodium before the ether on it evaporates,
and this saves him the time of measuring it out.
About 200 ml of the absolute alcohol is put in the sep funnel and the
valve opened to allow the alcohol to flow down onto the sodium metal. Cold
water should be flowing through the condenser. Magnetic stirring is not
necessary at this time, but the 2000 ml flask is sitting in a large pan. A
pail of cold water and a towel are kept handy. Sodium and alcohol react
together vigorously, and the alcohol boils like crazy. The condenser is
checked to see how far up the alcohol vapors are reaching. The chemist does
not want the alcohol vapors to escape out the top of the condenser. If the
vapors are making it more than halfway up the condenser, cold water is
poured from the pail into the pan the flask is sitting in. That cools it
off and slows down the boiling. But if that does not do enough, the wet
towel is put on top of the flask. When the boiling slows down, the towel
and the pan of water are removed, then more alcohol is added to the sep
funnel. A fresh ball of cotton is put in the top of the sep funnel to
protect the alcohol from water in the air. The alcohol is added to the
flask at such a Mte that the boiling of the alcohol continues at a nice
Mte. When all of the original one liter of absolute alcohol has been added
to the flask, the flask is gently heated on the hot plate to keep the
alcohol boiling until the little pieces of sodium are dissolved. If the
chemist has done a very good job, the result is a clear solution. If not,
it will be milkycolored.
The magnetic stirring is now begun, and 195 grams (190 ml) of
ethylacetoacetate is put in the sep funnel over the next 15 minutes. The
solution is heated to a gentle boiling. As it is boiling and stirring, 236
grams of bromobenzene is put in the sep funnel and dripped into it over a
period of an hour. The boiling and stirring is continued for 8 hours.
Then the stirring is stopped and the solution allowed to cool down. A
good amount of sodium bromide crystals settle to the bottom of the flask.
When they have settled to the bottom, the glassware is taken apart and as
much of the alcohol solution as possible is poured into a 3000 ml flask.
The last of the product is rinsed off the sodium bromide crystals by adding
about 50 ml of absolute alcohol to them, swirling around the mixture, then
filtering it. This alcohol is added to the alcohol in the 3000 ml flask.
The glassware is set up as shown in Figure 3 in Chapter 3. A 1000 ml
flask is used as the collecting flask. The alcohol in the 3000 ml flask is
heated. The oil in the pan is not heated above 115ΓΈ C. The distillation is
continued until the chemist has collected over 900 ml of alcohol in the
collecting flask.
When the alcohol has been boiled out, the heat is turned off and the
flask removed from the pan of oil. As it is cooling off, 1500 ml of 5%
sodium hydroxide solution is mixed. To do this, 75 grams of sodium
hydroxide is put in a flask and 1400 ml of water added. (Lye may be used as
a sodium hydroxide substitute.) When both the sodium hydroxide solution and
the reaction mixture near room temperature, the sodium hydroxide solution
is poured into the 3000 ml flask with the reaction mixture. The magnetic
stirring bar is put into the flask and magnetic stirring is begun. It is
stirred fast enough that a whirlpool develops in the mixture and the~beta
keto ester gets into contact with the sodium hydroxide solution. The
stirring is continued for 4 hours without heating the solution. The beta
keto ester reacts with the sodium hydroxide to produce the compound shown
above, plus ethyl alcohol. This is a hydrolysis reaction.
After 4 hours of stirring, the stirring is stopped and the solution
allowed to sit for a few minutes. A small amount of unreacted material will
float up to the top. If there is a large amount of unreacted material, the
stirring is begun again and 40 grams of sodium hydroxide and 300 ml of
isopropyl rubbing alcohol are added. It is stirred for 4 more hours. But
generally this is not necessary.
The unreacted layer is poured into a 1000 ml sep funnel. A good deal of
the sodium hydroxide solution will be poured off with it. The chemist lets
it sit for a few minutes, then drains the sodium hydroxide solution back
into the 3000 ml flask. The oily unreacted material is poured into a small
glass bottle and kept in the freezer. When a good amount of it has
accumulated, the chemist tries reacting it again with 5% sodium hydroxide
solution. However, this will not yield very much more product, because most
of this oily material is the diphenylacetone byproduct.
The underground chemist is now ready to produce phenylacetone. The
compound shown above will react with sulffiuric acid to produce
phenylacetone and carbon dioxide gas. He mixes up 150 ml of 50% sulffiuric
acid. To do this, he adds slightly more than 55 ml of sulfuric acid to
slightly less than 105 ml of water; if he added more sodium hydroxide and
alcohol to his reaction mixture, he mixes up twice as much 50% sulfuric
acid.
The stirrer in the 3000 ml flask containing the sodium hydroxide is
started up again. Then the 50% sulffiuric acid is slowly added to it. It
will bubble out carbon dioxide like crazy and crystals of sodium sulfate
will be formed. Phenylacetone will also be formed, some of it floating on
the surface of the solution, some of it trapped among the crystals formed.
When all of the sulffiuric acid has been added, and the bubbling of carbon
dioxide has slowed down to just about stopping, the stirring is stopped.
The glassware is set up as shown in Figure 3. The collecting flask is
2000 ml. The 3000 ml flask is slowly heated to boiling. The steam carries
the phenylacetone along with it to the other flask. This process is called
a steam distillation. The distilling is continued until a little more than
1000 ml is in the collecting flask. By then, almost all the phenylacetone
will be carried over into the collecting flask. There will be two layers in
the collecting flask, a yellow layer of phenylacetone on top, and a clear
water layer. There will be some acid dissolved in the water. Forty grams of
sodium hydroxide is dissolved in 150 ml of water, then added to the 2000 ml
flask. The flask is stoppered and shaken for one minute to destroy the
acid. Then 100 ml of benzene is added to the flask and it is shaken some
more. The phenylacetonebenzene layer is poured into a 1000 ml sep ffiunnel
and allowed to sit for a couple of minutes. Then the water layer is drained
off back into the 2000 ml flask. The phenylacetone layer is poured into a
500 ml flask along with a few boiling chips. Then 100 ml of benzene is
added to the 2000 ml flask, which is shaken again for about 30 seconds
before it is allowed to sit for a few minutes. The benzene layer is poured
into the 1000 ml sep funnel and allowed to sit for a couple of minutes. The
water layer is drained out, and the benzene layer is poured into the 500 ml
flask with the rest of the phenylacetone. The glassware is set up as shown
in Figure 5 and the phenylacetone distilled as described in Chapter 3. The
yield is about 125 ml of phenylacetone. (For more information on thisreaction, see Organic Reactions, Volume 1, published in 1942, page
266.)
Secrets of Methamphetamine Manufacture (3rd ed.)
by Uncle Fester
|
). So the answer is (as kavu already said) no. Furthermore, why do you think that
bromobenzene is very toxic or light sensitive? Iodobenzene is quite light sensitive, but bromobenzene is OK and only rated as "irritant" (also, I like
the odour
). 