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- The recrystallization and dissolution of acetylsalicylic...
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Ubc theses and dissertations, the recrystallization and dissolution of acetylsalicylic acid jamali, fakhreddin --> -->.
Observations that some samples of commercial acetylsalicylic acid had different dissolution rates were followed by reports that acetylsalicylic acid exists in more than one polymorphic form. The evidence for polymorphism has been questioned by a number of authors and the effects of such factors as crystal habit, particle size, crystal imperfection, the presence of salicylic acid and spherulites of acetylsalicylic acid have been discussed in an attempt to explain the anomalous behaviour. This work attempts to resolve the conflicting points of view. Acetylsalicylic acid was recrystallized from ethanol in a crystallizer which permitted control of the degree of supersaturation and, therefore, growth rate. In addition, a number of other recrystallization techniques and solvents were used to produce acetylsalicylic acid crystals with a wide variety of habits and varying amounts of salicylic acid. The crystals were compressed into discs both with and without prior size reduction and sieving. Intrinsic dissolution rates, measured using a rotating disc technique showed that the rates were independent of crystal growth rate, crystal size and habit, the content of salicylic acid (up to 3.8% w/w) and the presence of spherulites of acetylsalicylic acid. X-ray diffraction patterns revealed no differences between the various crystals and the original commercial material. Melting points, however, were dependent on the method of measurement and the crystal size and habit. Using the hot-stage method and heating at a rate of 0.2°per minute from a starting temperature of 2° below the approximate melting point (previously determined), acetylsalicylic acid melted, with decomposition, in the range of 128.3 to 132.7°, (excluding spherulites). When heating was started at 100° the melting range became very broad with small unaggregated particles starting to melt at temperatures between 103° and 112°. Analysis of the melt showed that the proportion of salicylic acid increased with decrease in particle size of the original acetylsalicylic acid crystals. Hence, the depression of the melting point of individual crystals is related to the increased susceptibility of small particles to thermal decomposition with the formation of salicylic acid. Evidence for the existence of metastable polymorphs of acetylsalicylic acid rests on the reported properties of needle-like crystals recrystallized from n-hexane and spherulites grown in thin films from saturated alcoholic solution. The needle-like crystals melted over the range 123.9° to 130.1° using a heating rate of 0.2° per minute from a starting temperature 2° below the approximate melting point. The wide melting range is probably due to decomposition of the fine needles and the formation of salicylic acid as discussed above. Spherulites of acetylsalicylic acid underwent a thermal transformation over the range 104° to 128° to form elongated prisms and a solution phase transformation into well defined prisms when in contact with a saturated solution of acetylsalicylic acid in various alcohols. The intrinsic dissolution rates of compressed discs prepared from the needle-like crystals and spherulites were the same as the other acetylsalicylic acid crystals. Moreover, X-ray diffraction patterns of the needle-like crystals, the spherulites and the crystals formed from the spherulites after thermal and solution phase transformation were identical with each other and the original aspirin. Hence, the needle-like crystals and spherulites are not metastable polymorphic forms of acetylsalicylic acid. It is suggested that both the thermal and solution phase transformation are growth processes.
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- UBC_1973_A6_7 J34.pdf -- 5.2MB
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Permanent URL: https://dx.doi.org/10.14288/1.0101415
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IMAGES
COMMENTS
Purpose: Purify salicylic acid by recrystallization, use melting points to compare the purity of crude and recrystallized material, and use infrared spectroscopy to confirm functional group transformation. In this experiment, you will recrystallize the salicylic acid you synthesized in a previous experiment.
Recrystallization of Salicylic Acid and Bromoacetanilide Recrystallization is one of the major techniques for purifying solid organic compounds. A pure organic compound is one in which there are no detectable impurities. By completing Experiment #2, you will master the technique starting with two compounds that are structurally different.
ORGANIC CHEMISTRY 121 EXPERIMENT 1 SYNTHESIS OF ASPIRIN FROM SALICYLIC ACID Aspirin is one of the oldest and most common drugs in use today. It is both an analgesic (pain killer) and antipyretic (reduces fever). One method of preparation is to react salicylic acid (1 ) with acetic anhydride (2) and a trace amount of acid (equation 1).
Objective: In this experiment you will learn to remove impurities from a compound by recrystallization.* First the best recrystallization solvent will be determined for the compound, then hot gravity filtration and vacuum filtration will be used to separate the compound from the impurities. The melting point range for the original and purified crystals will be determined in order to verify the ...
The aspirin collected will then be purified by recrystallization. In this purification method, the crude aspirin will be dissolved in a small amount of warm ethanol. Water will then be added and the solution will be cooled slowly and then chilled. The acetylsalicylic acid will recrystallize, and the solid impurities (unreacted salicylic acid) should remain dissolved in the solution. The solid ...
The reaction this reaction acetic hydride may be used in complete with water, The acetic acid is produced is removed by filtration of the acetic acid- water solution to yield aspirin crystals. Trace amounts of salicylic remaining are removed by recrystallization from an ethanol/water solvent pair. .
In this laboratory you will carry out the recrystallization of two organic compounds: benzoic acid and naphthalene. The first experiment gives you the opportunity to practice the technique by recrystallizing benzoic acid from a single solvent (water).
Salicylic acid recrystallization pre-lab solubility and recrystallization of salicylic acid: purpose: five compounds will be tested to see if they dissolve in
To understand the chemistry, the student must be able to recognize the common molecular framework shared by oil of wintergreen, salicylic acid, and aspirin and to identify the -OH and -CO 2 sites where chemical changes occur. The experiment differs in three ways from traditional aspirin synthesis experiments for general chemistry.
+ Synthesis of Aspirin in the world. Aspirin's chemical name is acetylsalicyl-ic acid, and it is synthesized from the reaction of acetic anhydride with salicylic acid in the presence of phosphoric acid s a catalyst. The by-product is acetic acid H3PO 4 → +
Salicylic Acid. Procedure: 1- Put 1 g of impure Salicylic acid sample in a beaker. 2- Try to dissolve it in a minimum amount of hot water with heating.
In this experiment, aspirin will be produced by reacting salicylic acid with acetic anhydride, a derivative of acetic acid that has similar chemicals properties to acetic acid, but reacts more rapidly and efficiently. to form acetylsalicylic acid (aspirin).
Experiment 6 Synthesis Of (Acetylsalicylic Acid)Experim. hesis Of Aspirin (Acetylsalicylic Acid)Purpose:The purpose of this experiment is to synthesize the common pain killer aspirin via an esterification reaction between Salicylic Acid and Acetic Anhydride in the presence of.
Acetylsalicylic acid was recrystallized from ethanol in a crystallizer which permitted control of the degree of supersaturation and, therefore, growth rate. In addition, a number of other recrystallization techniques and solvents were used to produce acetylsalicylic acid crystals with a wide variety of habits and varying amounts of salicylic ...
In this experiment, students carry out the acid-catalyzed esterification of salicylic acid with acetic anhydride and isolate aspirin as a white solid (Scheme 1).
The actual laboratory we will do is the recrystallization of benzoic acid from water using the temperature gradient method. Benzoic acid is not very soluble in cold water, but it is soluble in hot water. The purpose of this experiment is to learn the technique of recrystallization by purifying benzoic acid.
There are several types of recrystallization including single-solvent, multi-solvent, and hot filtration. The document provides details on these techniques and describes an experiment to purify salicylic acid by recrystallization using water as the solvent.
Preparation of salicylic acid from wintergreen oil Lab Report: Title: The practical experiment of preparing salicylic acid from wintergreen oil involves a series of chemical reactions, primarily the process of hydrolysis. Wintergreen oil, also known as methyl salicylate, is hydrolysed to produce salicylic acid and methanol. Abstract: This practical is important because it demonstrates a key ...
In this experiment, organic synthesis was performed in order to prepare for the synthesis of salicylic acid from methyl salicylate. The mechanism of the conversion of methyl salicylate to salicylic acid involved the formation of a bond between a hydroxide ion and a carbonyl (C=O) carbon atom and the breaking of a pi bond within the C=O.
Ye CX, et al. (2024). 2% supramolecular salicylic acid hydrogel vs. adapaline gel in mild to moderate acne vulgaris treatment: A multicenter, randomized, evaluator-blind, parallel-controlled trial ...
A systematic study on the batch cooling sonocrystallization of p-aminobenzoic acid (pABA) in ethanol was investigated under different ultrasound frequencies (22 kHz to 1 MHz), powers (1-40 W), and sonication times (1.73-31.85 min), with the crystal length, width, aspect ratio (AR), and induction time recorded for each experiment. These measured variables were related to sonoluminescence ...