Achieving Moderate Pressures in Sealed Vessels Using Dry Ice As a Solid CO₂ Source

This method can help address a key challenge in the field of synthetic organic chemistry, namely how to perform reactions under carbon dioxide atmosphere quickly and easily. The main advantage of this technique is that it allows reactions to be performed under carbon dioxide atmospheres above ambient pressures without the need for expensive, specialized equipment. Though this method can be useful for direct CH arylation it can also be applied to other reactions such as CH capitulation, or converting car epoxides into syntha carbonates.

Generally individuals new to this matter will struggle because they will fail to properly exfoliate the dry ice prior to addition or will take too long to seal the vile. To begin add a stir bar to a dry 7.5 milliliter vile and add 6.7 milligrams of palladium acetate to the vile. Next ad 99.9 milligrams of silver trifluoroacetate 92.3 milligrams of phenyl iodide and 26.3 milligrams of tert-amylamine to the vile.

Then add 1 milliliter of acidic acid and 21.7 microliters of deionized water to the vile. The key to success is to ensure that the appropriate amount of dry ice is added in a timely manner and that only dry ice not deposited water is added to the reaction vessel. After weighing out 26.3 milligrams of dry ice immediately add the ice and seal the vile with a PTFE lined cap.

Before setting up the reaction it is important to confirm a good fit between the cap and the vessel to prevent a traumatic loss of carbon dioxide pressure before or during the reaction. Stir the seal reaction vile for 15 minutes at room temperature. Then transfer the reaction vessel to a preheated 110 degree Celsius plate for a 14 hour stirring incubation.

The next morning open the vile after cooling to vent the CO2. To perform a reaction in a 7.5 milliliter vile with air excluded add a stir bar and the same reagents and solutions as just demonstrated to a dry 7.5 milliliter vile. After the deionized water has been added tear the vile on a balance and add approximately 98 milligrams of dry ice.

Allow the CO2 to sublimate off until a final mass of approximately 26 milligrams is achieved. Followed by immediate sealing of the file with a PTFE lined cap. Then stir the sealed reaction vile for 15 minutes at room temperature followed by an overnight stirring incubation at 110 degrees Celsius as just demonstrated.

To perform an air not excluded reaction in a 35 milliliter pressure tube add a stir bar to a dry 35 milliliter pressure tube. And add 6.7 milligrams of palladium acetate to the tube. Add 132.5 milligrams of silver trifluoroacetate 183.6 milligrams of phenyl idodide and 57.4 milligrams of the secondary amine starting material to the pressure tube as well as 1 milliliter of acidic acid and 1 milliliter of hexafluoroisopropanol Next add 21.7 milliliters of deionized water to the pressure tube followed by 1.32 grams of dry ice.

Immediately seal the tube with an appropriate Teflon screw cap. And stir the sealed reaction vessel for 15 minutes at room temperature. Then transfer the reaction vessel to a 90 degree Celsius hot plate for a 24 hour stirring incubation.

Upon cooling place a towel or padded glove over the cap and carefully open the pressure tube to vent the CO2. Under the 7.5 milliliter vile air not excluded reaction conditions two methyl for phenyl butanoate can be obtained as an oil at a 69 to 72 percent yield demonstrating a proton nuclear magnetic resonance spectrum consistent with the desired product. The reactions can also be performed in pressure reaction tubes.

Allowing the synthesis of two methyl and three methyl benzol four phenyl butanoate two amine at a 40 percent yield. While attempting this procedure it is important to remember to be quick while measuring out the dry ice. This technique will allow researchers in the field of synthetic chemistry to study reactions involving moderate pressure of carbon dioxide without the need for complicated and often expensive equipment increasing the number of reactions that can be run in parallel.

Don’t forget that working with pressurized vessels can be extremely hazardous and the precautions such as using blast shields or working behind hood sashes should always be taken while performing this procedure.