Technique used in structure determination of abetic acid
Answers
Answered by
0
The calculation of molar quantities is based on an acid number of 166 for N-grade wood rosin as obtained from Hercules Powder Company, Wilmington, Delaware. Acid number is the number of milligrams of potassium hydroxide required to neutralize 1 g. of sample.
2. Blanketing the rosin in solution or in the molten state with carbon dioxide serves to keep it out of contact with air to avoid oxidation.
3. The maximum negative optical rotation, [α]D24 −35°, is obtained with a minimum reflux time of 2 hours.
4. Rotations are reported as those of 1% solutions in absolute ethanol.
5. The addition of the amine to the hot solution is necessary for the formation of the salt. However, it must be done slowly and with rapid stirring because of the resulting vigorous exothermic reaction.
6. Commercial diamylamine, a mixture of isomers, purchased from Sharples Chemicals Company, Philadelphia, Pennsylvania, was employed.
7. The acid is added to a cooled solution of the salt in ethanol to minimize the chance for isomerization of the liberated abietic acid.
8. An early filtration is desirable for the purpose of removing the abietic acid from the acidic solution where isomerization can take place. Washing with a large volume of water and recrystallizing assures the complete removal of acetic acid.
9. The pure acid is dried in a vacuum desiccator over sodium hydroxide or calcium sulfate and stored in an oxygen-free atmosphere. Undue exposure to higher temperatures will result in isomerization, and contact with oxygen will result in oxidation.
10. The absorption spectrum data were obtained from measurements made with a Beckman Ultraviolet Spectrophotometer. The formulas employed in making the calculations use the term α, specific absorption coefficient. α = log10 I0/I/cl where I0 = intensity of radiation transmitted by the solvent; I = intensity of radiation transmitted by the solution; c = concentration of solute in grams per liter; l = length in centimeters of solution through which the radiation passes.
2. Blanketing the rosin in solution or in the molten state with carbon dioxide serves to keep it out of contact with air to avoid oxidation.
3. The maximum negative optical rotation, [α]D24 −35°, is obtained with a minimum reflux time of 2 hours.
4. Rotations are reported as those of 1% solutions in absolute ethanol.
5. The addition of the amine to the hot solution is necessary for the formation of the salt. However, it must be done slowly and with rapid stirring because of the resulting vigorous exothermic reaction.
6. Commercial diamylamine, a mixture of isomers, purchased from Sharples Chemicals Company, Philadelphia, Pennsylvania, was employed.
7. The acid is added to a cooled solution of the salt in ethanol to minimize the chance for isomerization of the liberated abietic acid.
8. An early filtration is desirable for the purpose of removing the abietic acid from the acidic solution where isomerization can take place. Washing with a large volume of water and recrystallizing assures the complete removal of acetic acid.
9. The pure acid is dried in a vacuum desiccator over sodium hydroxide or calcium sulfate and stored in an oxygen-free atmosphere. Undue exposure to higher temperatures will result in isomerization, and contact with oxygen will result in oxidation.
10. The absorption spectrum data were obtained from measurements made with a Beckman Ultraviolet Spectrophotometer. The formulas employed in making the calculations use the term α, specific absorption coefficient. α = log10 I0/I/cl where I0 = intensity of radiation transmitted by the solvent; I = intensity of radiation transmitted by the solution; c = concentration of solute in grams per liter; l = length in centimeters of solution through which the radiation passes.
Similar questions