Salicylic acid is a compound used in modern medicine and cosmetics, which faces numerous challenges due to its distinct chemical attributes. One of its properties, the melting point, tends to gather substantial attention from the scientific community. Knowing the melting point of salicylic acid often assists in its more effective formulation for clinical and industrial applications, including acne products. The present work aims to elaborate this property of melting point as a major characteristic of the compound, focusing on its impact in defining the thermal stability, solubility, and efficiency of the compound. This blog post unveils the different attributes of salicylic acid and serves every interested in chemistry, pharmaceutical formulation, and beyond. So get ready to dive into the realms where chemistry meets real-world utility.
What is Salicylic Acid?
Throughout the years, Salicylic acid has been useful to pharmaceutical and skincare industries because of its exfoliating qualities and inflammation-reducing properties. It is a beta hydroxy acid (BHA) and is known to effectively treat acne, psoriasis, and even warts. Salicylic acid is an extract of willow bark and can pass through the skin and assist in the shedding of dead skin cells, which unclogs pores, aiding in cell regeneration. Salicylic acid is versatile due to its antimicrobial and keratolytic properties which allows it to be useful in the medical and cosmetic fields.
Understanding the Molecular Weight and Chemical Structure
Salicylic acid has a molecular weight of 138.12 g/mol and a chemical formula of C7H6O3. The structure of salicylic acid contains a benzene ring and a carboxylic acid group (-COOH) functional group attached in the ortho position in addition to a hydroxyl functional group (-OH). With this configuration, salicylic acid qualifies as a beta hydroxy acid (BHA), which also enhances its lipid solubility and skin permeation efficacy.
Historical Background and Uses of Salicylic Acid
The use of salicylic acid dates back centuries, and it was utilized as far back as ancient times. Historically, willow bark (Salix spp.) was the source of salicin, which was used for pain relief and fever reduction. As these civilizations advanced, they were further able to document these remedies in texts from ancient Egypt through the works of the notable Hippocrates, who referred to it alongside easing inflammation and aches.
Salicylic acid itself was chemically isolated and seeing structural application through 19th century medicine and dermatology. It served as a powerful anti-inflammatory and keratolytic agent which eased the development of modern pharmaceuticals. Now regarded as a active compound in a plethora of over-the-counter and topical ointments, salicylic acid stands out for its use in acne, warts, and psoriasis treatments.
Incorporating recent advancements in biotechnology, there has been an expansion in the number of industries that utilize salicylic acid. As an example, its use as a beta-hydroxy acid makes it a prime component in skincare since it allows both exfoliation and pore cleansing. Supporting research makes its application promising; for example, dermatological research shows that salicylic acid concentration of 0.5-2% yields notable improvements in acne-prone skin when compared to other harsh topical treatments.
Moreover, in agriculture, the use of salicylic acid derivatives as Plant Growth Regulators is on the rise to boost resistance to stress and diseases in crops. It’s still undergoing research in areas like industrial chemistry, further demonstrating its usefulness in a range of applications.
Comparison with Acetylsalicylic Acid or Aspirin
While both salicylic acid and acetylsalicylic acid share a base structure, they differ greatly in their medical uses, chemical properties, and methods of action. As meta- and para-hydroxy derivatives of benzoic acid, their current forms, as used in modern medicine, are acetylated and incorporated in aspirin. Aspirin is primarily used to reduce pain, inflammation, and fevers in modern medicine.
When looking to synthesise aspirin, its father Figure, salicylic acid, acts as a starting point. The addition of an acetyl group to salicylic acid enables it to gain the ability to complete several important metabolic reactions by inhibiting cyclooxygenase (COX) enzymes. The inhibition of these enzymes results in the decreased production of prostaglandins that cause inflammation, pain, and fever. In contrast, salicylic acid is primarily useful in the medical field, where it serves as a keratolytic agent, exfoliating dead skin and unclogging pores through the destruction of intercellular bonds within the upper layer of the skin.
The systemic effects of aspirin certainly facilitate its usefulness in the maintenance of cardiovascular health. Its regular, low-dose administration, specifically at 81mg per day, is associated with a lower risk of heart attacks and strokes in high-risk individuals due to the drug’s antiplatelet or blood-thinning properties. On the contrary, salicylic acid does not exhibit such systemic effects as it seldom goes beyond the skin barrier. While aspirin is well-recognized as an internal medication, salicylic acid still reigns supreme in topical medicines for acne, psoriasis, and other skin disorders.
Like other therapeutics, aspirin bears specific safety considerations which should be carefully accounted for. Prolonged use or misuse tends to result in gastrointestinal irritation or ulcer due to the chronic blockade of protective prostaglandins in the gastric lining. While topical salicylic acid is largely safe, portending skin irritancy or dryness to some sensitive individuals, allowance remains for negative reputational effects. Governance on the application of each compound’s usefulness needs to consider the defined scope of each’s use and foreseeable side effects.
Both compounds, although part of the same chemical family, showcase differences in the usage that underline their versatile application in medicine and industry. The repose of salicylic acid in topical dermatology and agriculture starkly contrasts the place of aspirin as a systemic and critical medication for pain relief and managing cardiovascular disease.
Why is the Melting Point Significant?
Importance of Identifying Purity and Quality
A compound’s melting point is a vital physical property that indicates its level of purity or quality. Pure substances exhibit a definite melting point, and salicylic acid is no different, which indicates its high purity. Impurities, however, worsen the melting point by broadening the range and lowering it to indicate additives. For instance, pharmaceutical grade compounds are likely to have a relatively strict range within which their melting point lies, often quoted as 0.5˚C, signifying their high purity and compliance with pharmacological standards.
With advancements in technology, the accuracy of melting point determination for salicylic acid has improved due to monitoring changes in heat flow with temperature using differential scanning calorimetry (DSC). Such methods enable scientists to monitor minute changes brought about by impurities, enhancing quality control criteria. Moreover, in industrial processes such as polymer manufacturing, monitoring melting points during production guarantees that the correct thermal and mechanical properties are achieved.
Precise melting point determination remains critical to the synthesis and characterization of unfamiliar compounds. For example, a documented melting point ensures reproducibility, which helps verify the materials’ identity and structure confirmation. This property is crucial from pharmaceutical research to materials science, where purity influences performance and efficacy.
The Role in Synthesis and Chemical Reactions
Melting points are important when establishing the parameters of a chemical reaction, particularly in its synthesis. For instance, during the recrystallization stage, the melting point is critical in determining the solvents and the conditions for maximum yield and optimal purity. Additionally, a compound’s melting point serves as a measurement of its thermal stability, which is critical in heat-dependent reactions. Evidence indicates that greater purity leads to sharper melting points, while broader or depressed ranges of melting signify the level of impurity, thus functioning as an evaluation method for the degree of purification attained.
In many cases, multi-step chemical processes require verification through assessing the control of the experiment by analyzing the melting point of the determined products. As an example, in pharmaceutical crystal engineering, distinguishing polymorphic forms of active pharmaceutical ingredients (APIs) is done meticulously through precise measurements of melting points to ascertain consistency and bioavailability. High precision concerning their melting points is achieved using advanced methods such as differential scanning calorimetry (DSC). Analysis of thermal behavior becomes simpler and more reliable with lower confusion regarding the sharply defined ranges of melting points. The focus on such thermal properties by various industries demonstrates the need for studying melting points analysis regarding chemical synthesis and processes.
Influence on Properties of Salicylic Acid
The melting point of salicylic acid impacts its stability, purity, and overall effectiveness in different applications. Melting point consistency and narrowness indicate salicylic acid purity, which is imperative in pharmaceutical and cosmetic applications. Deviations from this set melting point imply the presence of some impurities or structural deficiencies, which may alter its solubility as well as reactivity. Harnessing and controlling this property leads to performance and dependable products for users.
How is the Melting Point of Salicylic Acid Measured?
Standard Methods and Equipment Used
The melting point of salicylic acid is usually measured with a melting point apparatus. This device heats the sample slowly and monitors the temperature at which it transitions from a solid to a liquid. According to standard methods, salicylic acid is first placed into a capillary tube, and then the tube is put in the apparatus. The temperature is noted at the commencement and conclusion of the melting process. The device must first be calibrated with known reference substances to ensure accuracy. The reliability of these methods reinforces quality control and product consistency.
Variations in Degrees Celsius and Factors Affecting It
The melting point of salicylic acid ranges from 158 °C to 161 °C at 158 °C, and it may change due to several reasons. A sample’s impurities, for instance, have noticeable effects by lowering the melting point and increasing the phase transition range. This melting point depression happens due to lattice structures being melted instead of removed.
High nonlaboratory pressures usually result in phase change behavior alteration, however, these shifts are miniscule within a laboratory setting. As a rule of thumb, increased pressure raises the melting point while decreased pressure drops it.
Increasing eases of over calibration or a lack of proper maintenance in melting point measuring devices also resists the accuracy of the reading. Regular calibration with clearly defined melting point substances like benzoic acid (122.4° C) and vanillin (81 °C) greatly improves precision.
Emerging information indicates that improvements to digital melting point detectors increase the precision and reproducibility of the systems and reduce the possibility of human error in recording the temperature. This information also aids the case for standardization in fields such as drug and chemical manufacturing, where the evaluation of quality is essential.
Reference Standards: National Institute of Standards and Technology
For accuracy in melting point measurements, NIST’s certified reference materials and calibration guidance are invaluable. To preserve uniformity, I suggest following their documented procedures along with measuring against appropriate reference standards.
What are the Properties of Salicylic Acid?
Solubility and Reactions with Water
Salicylic acid has low solubility in water. At room temperature, around 2.2 grams of salicylic acid will dissolve in 1 liter of water. When mixed with water, it does not completely dissolve and only forms a suspension. This is because the carboxylic acid group paired with the phillic aromatic ring greatly reduces the compound’s ability to interact with water. Nevertheless, in alkaline conditions, where salicylic acid can react with water to form salicylate salts, its solubility drastically increases.
Interaction with Salts and Esters of Salicylic Acid
Salicylic acid’s versatility extends to the salts and esters of the acid, as well as the derivatives of those compounds, which have various uses across the pharmaceutical and cosmetic industries. The esters and salts of salicylic acid undergo different reactions to clean the respective functional groups. For instance, sodium salicylate, which is a salt of salicylic acid, is known to be water soluble and has anti-inflammatory as well as analgesic effects. These salts can improve bioavailability in solutions, which enhances formulation in aqueous solutions.
Methyl salicylate, also known as oil of wintergreen, is an ester of salicylic acid that is synthesized by esterification of the hydroxyl groups in salicylic acid. It is widely known to be used in topical soothing ointments for pain relief due to its anti-inflammatory properties. Another widely known ester and Ayurvedic medicine is acetylsalicylic acid (aspirin), which is synthesized by reacting salicylic acid and acetic anhydride. This important compound has powerful effects in medicine as it is antipyretic, analgesic, and antithrombotic. It is one of the most consumed pharmaceutical drugs across the world.
These changes made to the compounds display the many different ways salicylic acid can be used in medicine and pharmaceuticals and how those transformations need to go through for adjustment of solubility, reactivity, and therapeutic uses.
Effect of High Doses and Applications
Wide-Ranging Consequences
A high dose of a derivative of salicylic acid, for example, aspirin, will possess both a therapeutic effect as well as an adverse effect. When the dosage is low to moderate, it aids in alleviating pain, swelling, and even fever; however, in excess, it could lead to a condition known as salicylism. This is a condition in which one suffers from ear ringing (Tinnitus), dizziness, and nausea, and in severe cases, it could even lead to metabolic acidosis or respiratory alkilosis.
Information regarding the impacts of high doses:
- Toxicity Range: Signs or symptoms of toxicity start appearing at levels above 50 mg/dL on average.
- Lethal Dose: For adults, an average of 150 mg/kg of body weight is enough to be toxic without medical intervention.
Applications
Beauty and health industries, as well as cosmetics, make use of salicylic acid derivatives. Its major applications include:
Pharma Applications:
- Analgesi: In medicine, it’s widespread use includes alleviating mild to mid range inflammation as well as pain.
- Anti-inflammation: Blood clots are countered with low doses of aspirin, hence reducing risks of stroke and heart attacks.
- Derma: Known to treat acne, psoriasis, and warts by virtue of it being keratolytic, salicylic acid is widely known in the cosmetic world.
- Cosmetic Treatments Of Salicylic Acid has proven to be effective in the treatment of several skin conditions.
- Cosmetic Treatments Salicylic Acid functions as an exfoliating agent. It is included in facial washes and creams to help with skin rejuvenation.
Industrial Use:
Methyl salicylate, an ester derivative of salicylic acid, is, for instance, used as a flavoring and in the perfume industry.
These examples of the effects of salicylic acid and its derivatives show the importance of dosing and chemical changes with regard to safety.
How does Salicylic Acid Compare to its Derivatives?
Transformation to Acetylsalicylic Acid and its Uses
The conversion of salicylic acid into acetylsalicylic acid, also known as Aspirin, is one of the most acetylation-based chemical procedures in acyclic compounds. This occurs when salicylic acid is combined with acetic anhydride to form acetylsalicylic acid, an anhydride derivative of salicylic acid, with acetic acid released as a by-product. As with many other important acid-catalyzed reactions, the use of an acid catalyst, sulfuric acid or phosphoric acid, is required to speed the reaction. This is a straightforward approach to a very efficient form of synthesis developed in the late eighteen hundreds.
Acetylsalicylic acid still stands as one of the most widely studied and utilized drugs across the globe. Its primary medical application lies in its ability to ease pain, reduce inflammation, and lower fever. In addition to such application, there are many other recommendations of the medication such has positive value as an antiplatelet therapy, which greatly sinks the chances of thrombus formation. Recent research indicates that the administration of aspirin in low dosage regularly may lower the risk of myocardial infarction up to twenty-five percent in patients suffering from an existing cardiovascular disorder.
The protective forces acetylsalicylic might have on particular patients is another aspect of current research. For instance, new research has looked at the possibility of acetylsalicylic acid in lowering the chances of developing colorectal cancer for those with an increased genetic susceptibility. The findings suggest that possible long-term use with some medical supervision may lead to lowering the incidence of colorectal cancer by approximately fifteen to twenty percent.
Despite the therapeutic merits of acetylsalicylic acid, its administration warrants care due to potential side effects. In some individuals, common side effects may irritate the digestive tract and result in ulcer formation, as well as increased bleeding tendencies. Thus, its effectiveness and safety in treatment are always relative to optimal and precise dosing, as well as proper medical counsel. The process involved in converting salicylic acid to its acetyl form is still considered a landmark achievement in medicinal chemistry, melding natural compounds with the requirements of modern drugs.
Comparison with Sodium Salicylate and Methyl Salicylate
Aspirin, methyl salicylate, and sodium salicylate are all derivatives of salicylic acid; however, each exhibits unique pharmacological features. A salt that dissolves in water, sodium salicylate is mainly an anti-inflammatory and pain-relieving agent. It is considered milder than acetylsalicylic acid, which means its use is more suitable for people likely to suffer from gastrointestinal side effects from aspirin use. On the downside, sodium salicylate does not sufficiently inhibit platelet aggregation, which makes it unsuitable for use in heart disease preventive therapy.
Methyl salicylate, on the other hand, is used in topical creams and ointments for the relief of musculoskeletal pain. It belongs to the class of medicines known as counterirritants. Methyl salicylate acts as a topical agent by producing a heating or cooling effect on the site to relieve pain. Due to its possible toxic effects upon oral intake in large doses, methyl salicylate is not used systemically. Recent studies raise concerns on the use of high-concentration methyl salicylate products, especially in children, due to the risk of salicylate poisoning.
The clinical uses of these compounds are distinct, differing from one another. Acetylsalicylic acid, or aspirin, is well-documented for the preventive cardiovascular and colorectal cancer benefits it offers. On the other hand, sodium salicylate does not have strong evidence supporting such wide-reaching effects, although it can be useful in treating pain complications associated with inflammation in cases of aspirin sulfa allergy. Treatment with methyl salicylate is mostly non-systemic, and the focus of its use is on pain relief for conditions like arthritis or sprains.
The choice of treating using a salicylate form depends greatly on the individual’s specific medical needs, their level of tolerance, and the documented risks. Research continues to optimize the appreciation of these compounds, broadening their use in perfectly tailored treatment protocols.
Other Derivatives: Aminosalicylic Acid and Their Applications
Para-aminosalicylic acid, more commonly known as PAS, is one of the major derivatives of salicylic acid, and its particular application focuses on treating tuberculosis (TB). It was first proposed as a pharmaceutical treatment in the 1940s, making it one of the first antibiotics effective against Mycobacterium tuberculosis. Although PAS was once a cornerstone in the treatment regimen for TB, its frontline use has significantly decreased due to the emergence of advanced therapies. However, it remains an important part of the treatment for multidrug-resistant tuberculosis (MDR-TB). A detailed description of its use follows below:
Treatment of Multidrug-Resistant Tuberculosis (MDR-TB)
- In cases where there is known resistance to isoniazid and rifampicin, PAS serves as a second-line agent for MDR-TB.
- PAS works as a competitive inhibitor of dihydrofolate reductase and, therefore, inhibits folate synthesis in the bacterial cell, halting its growth and replication.
- PAS as a part of combination therapy has been shown clinically to be effective in reducing the bacterial burden along with other antimicrobial agents.
Treatment of Leprosy (Limited Role)
- PAS is not a primary treatment for leprosy, but some works attempt to address the lack of research concerning its application in cases with dapsone resistance.
- There is little evidence supporting its effectiveness in this regard, hence its restricted use.
Potential Anti-Inflammatory Activity (In Development)
- New studies are looking into the usefulness of aminosalicylic acid derivatives for the treatment of inflammatory diseases like inflammatory bowel disease (IBD). Such applications are still under investigation, and studies are needed to support these claims through clinical trials.
Use in Combination Treatment of Resistant Bacterial Pathogens
- PAS is also being studied for use in other resistant bacterial infections beyond tuberculosis, especially for use in combination with new classes of antibiotics to address intricate resistance mechanisms.
Important Data and Important Issues:
- Dosage: For the treatment of MDR-TB, PAS is usually prescribed in a daily dosage of 8–12 g, divided into several doses to make tolerating the medication easier for the patient.
- Side Effects: Gastrointestinal symptoms such as nausea, vomiting, and diarrhea, as well as more serious hypersensitivity symptoms like rash or fever, often accompany the treatment.
- Drug Interactions: Fluoroquinolones or rifampicin are some of the other drugs whose use with PAS poses scheduling conflicts due to possible absorption interactions.
The field is progressing PAS’s integration into strategies for drug-resistant infectious diseases on a global scale, all while development in the antimicrobial research world continues to expand.
Frequently Asked Questions (FAQs)
Q: What is the melting point of salicylic acid (CAS: 69-72-7)?
A: The salicylic acid (2-hydroxybenzoic acid) melting point is about 158 to 160 degrees Celsius. This property is important in the identification as well as the characterization of the compound, which finds extensive use in multiple applications.
Q: What are the key properties of salicylic acid?
A: Salicylic acid (69-72-7) is a white crystalline organic compound having a number of significant properties. Its melting point is in the range of 158-160 degrees Celsius; it is only slightly soluble in water, while salts of salicylates are formed. Furthermore, it has anti-inflammatory, exfoliating, and antimicrobial properties which makes it beneficial for use in skin care and medicines.
Q: How does salicylic acid behave in an aqueous solution?
A: Salicylic acid’s behavior in aqueous solution is that it partially dissociates into its ionic form. The concentration of salicylic acid in water has an effect on its behavior, with the more concentrated solutions being more acidic. It must be remembered, however, that salicylic acid has low solubility in water which has a bearing on its usefulness and formulation.
Q: What are some common uses of salicylic acid?
A: Salicylic acid is readily available and has numerous applications. It’s frequently found in dermatological products to address acne and inflammation, as well as dead cell exfoliation. It’s also a pharmaceutical agent for the treatment of warts, corns, and other dermatological disorders. Additionally, salicylic acid can also be used as a starting material for preparing aspirin (acetylsalicylic acid) by reaction with the acetyl group.
Q: How is salicylic acid produced?
A: There are diverse ways through which salicylic acid can be produced. One of the most common processes is the Kolbe-Schmitt reaction, in which sodium phenoxide is reacted with carbon dioxide under high pressure and temperature. The hydrolysis of methyl salicylate, which is obtained from the plant wintergreen, is another route. Initially, it was isolated from the bark of willow trees, which has a chemical called salicin, which is a natural source of salicylic acid.
Q: What is the relationship between salicylic acid and aspirin?
A: Salicylic acid is a parent compound of aspirin (acetylsalicylic acid) because it is formed from salicylic acid. Aspirin is produced from salicylic acid and an acetyl group brought to the reaction site by acetic anhydride. Both compounds serve similar purposes as anti-inflammatory and analgesic agents, but aspirin is less harmful to the gastrointestinal tract, which allows it to be taken orally.
Q: Are there any side effects associated with using salicylic acid?
A: Salicylic acid is normally regarded as safe when applied properly. However, side effects may be experienced, particularly if the application is done for a prolonged time or at high concentrations. The most common effects are secondary to irritant dermatitis, which is skin irritation, dryness, and peeling. In some instances, excessive use may result in salicylate toxicity, especially in cases where significant quantities are absorbed through the skin or ingested orally. It is advisable to follow the instructions of use and seek healthcare help where necessary.
Q: Is it true that other skincare components can be combined with salicylic acid?
A: Indeed, while it is possible to combine salicylic acid with other skincare components, it is important to be careful. It may work well with other compounds, such as glycolic acid, which enhances exfoliation. But combinations with benzoyl peroxide and retinoids, which could be overly irritating, may heighten the chances of skin irritation. Salicylic acid is best introduced to other new products over time, and a dermatologist’s advice is necessary on how to combine these ingredients.
Reference Sources
1. Title: Synthesis and Characterization of Some Tetrazole Derivatives From 5-Amino Salicylic Acid
- Authors: H. Chfat and H. T. Ghanim
- Journal: International Journal of Research
- Date of Publication: January 22, 2017
- Citation Token: (Chfat & Ghanim, 2017, pp. 677–684)
Summary:
- This work is dedicated to the synthesis of tetrazole derivatives from 5-amino salicylic acid. During the characterization phase, the melting points of the synthesized compounds were determined.
- As part of this study, several synthetic routes including the synthesis of azo compounds and their further transformation into tetrazole derivatives were carried out. Characterization utilized FT-IR spectroscopy, as well as 1H and 13C NMR spectroscopy, and melting point determination.
2. Title: The Biological Effects Of Some Compounds With Salicylic Acid And Cephalexin On Bacteria About First Series Of Transition Metals
- Authors: ABD ALKADIR MUHAMED ABD ALKADIR, Et Al.
- Year Of Publication: 2016
- Citation Identifier: (Adel Kadir Et Al. 2016 Pg 250 – 272)
Overview:
- In this paper, the authors described the preparation of metal complexes of salicylic acid and the physicochemical properties of these complexes which includes the determination of the melting points.
- Methodology: The research was based on the synthesis of complexes with several transition metals which were characterized by FT-IR, UV-Vis spectroscopy and by determining the melting points.
3. Title: Synthesis of Mutual Prodrug of p-Amino Salicylic Acid (PAS) and Isoniazid (INH) with Enhanced Physicochemical Properties
- Authors: A. Qasir, A. D. Jassim
- Published in: Journal of Al-Nahrain University-Science
- Publication Date: September 1, 2010 (not within the last 5 years but still relevant)
- Citation Token: (Qasir & Jassim, 2010, pp. 7–13)
Summary:
- The work involved the synthesis of a p-amino salicylic acid-doxybenzamine prodrug, of which the melting point was measured and used for characterization.
- Methodology: The synthesis was accomplished by performing amidation of the starting compounds. The products were characterized by measurement of melting point, TLC, and infrared spectroscopy.
4. Salicylic acid
5. Acid
