Notes on previous efforts in preparation of formaldehyde. . .
Because it is possible to produce small amounts by dipping a red hot copper wire into methanol, it was believed that keeping a wire slightly above the liquid might allow continuing production of formaldehyde in a self-sustaining reaction. Results of testing this method in a variety of configurations were disappointing, however. An old organic chemistry textbook suggested that this process must be carefully controlled in terms of temperature and airflow, to be successful and avoid explosions. Because a fairly complicated apparatus was employed it was decided that this method was not very practical for present purposes.
An alternative method was attempted, the details of which follow. An important background detail is that methanol, being highly polar, readily absorbs microwave energy.
A standard microwave oven was modified by cutting a small hole through the top of the cooking chamber, large enough to accommodate 1/4" glass tubing, which would be routed from the cooking chamber to the outside of the oven.
A piece of 1/4" flint glass tubing was bent to facilitate routing from the top of a flask placed inside the microwave oven to a point on top, exterior to the oven. A balloon was taped securely over the open end of the tubing.
Approx. 5ml of methanol was added to a 125ml Erlenmeyer flask. A very thin piece of copper wire roughly 12 inches long (from a small electric motor) was sanded to remove the lacquer insulation, then wrapped around a small nail. The coiled wire was removed from the nail and added to the flask containing methanol. Approx. 100 mg of powdered copper was also added to the flask.
The flask was placed in the microwave oven, and the glass tubing was fitted to the flask with a rubber stopper. The area of the rubber stopper was wrapped with aluminum foil to prevent it from melting, ensuring that all foil edges were flattened against the flask. The oven door was closed and the power was set to high. The oven was energized, with a constant watch on the balloon. As soon as it inflated to a size indicating significant pressure buildup the oven was stopped. The flask was allowed to cool enough that most of the pressure was relieved, then the process was repeated about a dozen times. Each cycle of microwave "on time" was ten seconds or less, except for the very first which may have taken a few additional seconds to begin.
When the flask had cooled completely it was removed from the oven and the contents examined. Surprisingly it was found that the liquid had taken on a slightly yellow color. Although it was expected that the MeOH would be converted to formaldehyde, the odor was more like that of an ester, and while familiar, the name was unknown.
It is believed that the cause of this anomaly may have been cooking too long. AT the outset it was not recognized that it might be possible to carry the oxidation too far, assuming that is what happened, and the extended cooking time was thought to increase the odds of success in forming formaldehyde.
Any input on what might have actually been created during this reaction and how it might best be modified will be most welcome.
PP
Because it is possible to produce small amounts by dipping a red hot copper wire into methanol, it was believed that keeping a wire slightly above the liquid might allow continuing production of formaldehyde in a self-sustaining reaction. Results of testing this method in a variety of configurations were disappointing, however. An old organic chemistry textbook suggested that this process must be carefully controlled in terms of temperature and airflow, to be successful and avoid explosions. Because a fairly complicated apparatus was employed it was decided that this method was not very practical for present purposes.
An alternative method was attempted, the details of which follow. An important background detail is that methanol, being highly polar, readily absorbs microwave energy.
A standard microwave oven was modified by cutting a small hole through the top of the cooking chamber, large enough to accommodate 1/4" glass tubing, which would be routed from the cooking chamber to the outside of the oven.
A piece of 1/4" flint glass tubing was bent to facilitate routing from the top of a flask placed inside the microwave oven to a point on top, exterior to the oven. A balloon was taped securely over the open end of the tubing.
Approx. 5ml of methanol was added to a 125ml Erlenmeyer flask. A very thin piece of copper wire roughly 12 inches long (from a small electric motor) was sanded to remove the lacquer insulation, then wrapped around a small nail. The coiled wire was removed from the nail and added to the flask containing methanol. Approx. 100 mg of powdered copper was also added to the flask.
The flask was placed in the microwave oven, and the glass tubing was fitted to the flask with a rubber stopper. The area of the rubber stopper was wrapped with aluminum foil to prevent it from melting, ensuring that all foil edges were flattened against the flask. The oven door was closed and the power was set to high. The oven was energized, with a constant watch on the balloon. As soon as it inflated to a size indicating significant pressure buildup the oven was stopped. The flask was allowed to cool enough that most of the pressure was relieved, then the process was repeated about a dozen times. Each cycle of microwave "on time" was ten seconds or less, except for the very first which may have taken a few additional seconds to begin.
When the flask had cooled completely it was removed from the oven and the contents examined. Surprisingly it was found that the liquid had taken on a slightly yellow color. Although it was expected that the MeOH would be converted to formaldehyde, the odor was more like that of an ester, and while familiar, the name was unknown.
It is believed that the cause of this anomaly may have been cooking too long. AT the outset it was not recognized that it might be possible to carry the oxidation too far, assuming that is what happened, and the extended cooking time was thought to increase the odds of success in forming formaldehyde.
Any input on what might have actually been created during this reaction and how it might best be modified will be most welcome.
PP