The rosario coolant It is a material designed by Felix Allihn, which presents a series of bubbles inside with the aim of increasing the surface in contact with the water that circulates through the outer chamber. Thus, the transfer of heat from the interior of the bubbles to the water is increased, ensuring efficient condensation of the solvent vapors..
The appearance of the coolant, due to the presence of the bubbles, suggested the names of rosary or ball coolant. It is also called Allihn's refrigerant.
Allihn designed his coolant as a response to a straight-wall, Liebig-type coolant problem. This refrigerant or condenser was not efficient in low-boiling solvents, such as ether. Allihn's solution was simple: increase the internal surface, by the presence in the internal tube of a series of bubbles.
The two most commonly used refrigerants in reflux devices are the rosary refrigerant and the coil refrigerant, also called Graham's refrigerant..
Although rosary coolant is generally used, with very low boiling point solvents it is convenient to use coil coolants as they provide more efficient cooling. This is the case of diethyl ether, with a boiling point of 35 ºC, and pentane (35-36 ºC).
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The mouth of the flask, usually made of ground glass, fits over one of the mouths of the refrigerant. The assembly is done in such a way that the refrigerant is vertical (upper image).
It is recommended that the water enters the external part of the coolant through a rubber or plastic hose, connected to its lower part. The water runs through the entire part that surrounds the inside of the coolant and exits through its upper part, ensuring greater heat transfer to the water..
Heating the flask with the solvent and the reagents is done using a heating plate or a blanket for the same purpose. These devices have a mechanism to regulate the amount of heat they supply.
As the solvent heats up, it begins to form vapor, which rises up the top of the heating flask until it reaches the refrigerant..
As it travels through the refrigerant, the solvent vapor comes into contact with the internal walls of the refrigerant, beginning its condensation..
The condensation is due to the fact that the internal wall of the condenser in the form of bubbles is in contact with the circulating water in the external refrigerant chamber..
The water prevents the temperature of the internal wall from increasing, keeping it constant and thus allowing the temperature of the steam entering through the refrigerant to decrease..
As the solvent vapor condenses and returns to its liquid state, the solvent droplets slide from the refrigerant into the heating flask..
By means of this procedure the loss of solvent through leaks in its gaseous state is minimized. In addition, it is about ensuring that the reaction that is occurring in the flask is at constant volume..
The rosario refrigerant is recommended in those reactions that occur at a temperature higher than the ambient temperature, since under these conditions a significant volume of the solvent would be lost if there was no adequate condensation of its vapors..
By continuously cooling the solvent vapor returned to the flask as a liquid, the reflux method allows the heating of the chemical reaction medium for a long time, increasing the efficiency of the reaction..
Many organic compounds have low boiling points, so they do not allow them to be subjected to high temperatures, as they would evaporate. If a refrigerant is not used, the reaction would not proceed completely.
Reflux allows the reaction temperature to be increased as is done in an organic synthesis, favoring an increase in the reaction rate.
In addition to water, other fluids are used in condensers or refrigerants; such as refrigerated ethanol, which can be thermostatically cooled.
The use of liquids other than water allows the coolant to cool down to a temperature below 0 ° C. This allows the use of solvents such as dimethyl ether, with a boiling point of -23.6 ºC..
The rosary refrigerant is used mainly in reflux, favoring the performance of reactions that require heating. But the same device can be used in simple distillation processes.
Distillation is the process used to separate a pure liquid from a mixture of liquids with different boiling points. For example, distillation is often used to separate ethanol from water..
Different liquids have different cohesion forces. Therefore, they have different vapor pressures and boil at different temperatures. The components of a mixture of liquids can be separated by distillation if their boiling points are sufficiently different..
The vapors of the liquids, product of the heating, condense in the refrigerant and are collected. First, the liquid with a lower boiling point boils, once the purified liquid has been condensed and collected, the distillation temperature is gradually increased and the liquid components of the mixture are collected..
The use of the reflux method has been used in the isolation of substances, for example: using the solid-liquid extraction technique it has been possible to obtain the active principles from plant tissues.
The solvent is refluxed and upon condensation falls onto a porous cartridge containing the processed sample. As evaporation occurs, solvent accumulates with the components of the plant tissue to be purified..
-Direct reflux extraction has been used in the extraction of fatty acids. Ethanol and 30 g of the analyte are used, heating the solvent in a flask. Reflux is carried out for 45 minutes to extract the fatty acids. The yield was 37.34%.
-In the synthesis of simple esters such as ethyl acetate, by combining reflux, simple distillation and distillation with rectification.
-Rosary coolant has been used in the reaction of incorporation of bromine to alkenes in boiling water. However, there has been loss of Br in this reaction.
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