Jimchem
some chemistry topics
Tuesday, August 27, 2024
LAWS OF THERMODYNAMICS
Sunday, August 18, 2024
THERMODYNAMICS
The word ‘thermodynamics’ is derived from two words: thermo and dynamics. ‘Thermo’ stands for heat while ‘dynamics’ is used in connection with a mechanical motion which involves ‘work’.
Broadly speaking, thermodynamics is a branch of science that deals with heat, work and temperature, and their relation to energy, radiation and physical properties of matter. It explains how thermal energy (heat energy) is converted to other forms of energy and how matter is affected by this process.
Different Branches of Thermodynamics:
- Classical Thermodynamics
- Statistical Thermodynamics
- Chemical Thermodynamics
- Equilibrium Thermodynamics
THERMODYNAMIC TERMS AND BASIC CONCEPTS:
Thermodynamic Systems:
Open System –
Closed System –
Isolated System –
THERMODYNAMIC PROCESS:
REVERSIBLE PROCESS:
IRREVERSIBLE PROCESS
Isothermal Process
Examples:
Adiabatic Process:
Examples:
Thursday, August 15, 2024
PURIFICATION TECHNIQUE - I
Dear students,
It is known that organic compounds can be derived from natural sources and these are mixed with other substances and are impure. Similarly compounds prepared in the laboratory are also mixed with other by products formed during the course of the reaction. To purify such compounds, various methods are adopted. Some of the common methods are as follows
Crystallization
Sublimation
Distillation
Extraction
Chromatography
In this post we are about to discuss two methods of purification. They are as follows.
Solvent Extraction:
Extraction means drawing (pulling out) a compound out of a mixture using a solvent. It means organic compounds have a "choice" of two solvents that they can dissolve in. It requires two solvents that are not miscible in each other. Usually one of the solvents is water. The other solvent is a liquid that does not dissolve very well in water, such as diethyl ether.
The process of removing organic substance from its aqueous solution by mixing with suitable organic solvent is termed solvent extraction. It is also called as liquid-liquid extraction and partitioning. It is an equilibrium process and is a convenient technique can be carried out using separating funnel.
Principle of Solvent Extraction
It is based on the fact that different substances have different solubility in different solvents.
Procedure:
The aqueous solution of the given solute (organic substance) is taken in a separating funnel. It is mixed with the organic solvent. The funnel is closed, and its contents are shaken well. It is then allowed to remain undisturbed for some time. Water and organic solvent will form separate layers, and the solute will be transferred from aqueous layer to the organic layer. In the funnel, the solvent forms the upper layer while the water forms the lower layer. The two layers can be recovered by opening the stop cock and collecting them in separate bakers. On evaporating the organic solvent, the solute can be recovered.
It is important to note that extraction is more efficient (i.e., higher purification) when the process is repeated. For example, benzoic acid can be extracted from its water solution using benzene.
Applications:
It is used in perfumes, vegetable oil, biodiesel processing, etc.
It is used to segregate hazardous contaminants from sludge and sediments.
In the petrochemical industry, it is used to separate and purify different components of crude oil.
It is used for the separation and purification of organic compounds.
It removes oil and grease that spilled into water. This helps clean up environmental pollution.
Crystallization:
It is a purification technique used to separate solids from a solution. In this method, the impurities are dissolved in a suitable solvent and then filtered to remove impurities.
Principle:
An impure organic solid is completely dissolved in a small amount of solvent by boiling. The hot solution is allowed to cool slowly. The impurities remain in the solution (called the "mother liquor") while the organic substance comes out as pure crystals . It is then filtered and dried.
Procedure:
Step 1: Take some water in a beaker
Step 2: Add organic substance (impure) and stir it
Step 3: Now heat the solution
Step 4: Add more impure substance.
Step 5: After some time there will be a point at which no more substance can be dissolved in water. This stage is the saturation point, and the solution is referred to as a saturated solution
Step 6: Now filter the substance with the help of a filter paper
Step 7: Collect the filtrate in a glass bowl and cool it slowly
Step 8: You will observe that some fine crystals are formed in the bowl
Step 9: The process of filtration can separate these crystals.
Selection of solvent:
(a) It dissolves more of the substance at higher temperature than at room temperature
(b) The impurities are either insoluble or dissolve in solution (in the mother liquor) upon crystallization,
(c) which is not highly inflammable and
(d) which does not react chemically with the compound to be crystallized.
The most commonly used solvents for crystallization are: water, alcohol, ether, chloroform, carbon- tetrachloride, acetone, benzene, petroleum ether etc.
Fractional crystallization:
Examples:
SEPARATION AND PURIFICATION TECHNIQUES
Methods of Separation:
Methods Of Separating Mixtures:
- Evaporation
- Filtration or Sedimentation
- Separating Funnel
- Magnetic Separation
Evaporation
Filtration or Sedimentation:
Separating Funnel
Magnetic Separation:
Monday, August 12, 2024
ANESTHETICS
What Is Anesthesiology?
Anesthesiology is an important branch of medicine as it makes surgery safe, feasible and possible. During and after surgery the patient feel the pain and discomfort hence they may be given anesthesia.
Anesthetic is basically a medicine that acts as a sedative. The term anesthesia means loss of sensation. It produces loss of sensation to all types of cells and especially those of nervous sysem.. The important aspect of anesthetics are the loss of consciousness is reversible.
Types:
1. General - complete loss of consciousness all over the body.
2. Local - lack of sensation in the area being operated on.
Ether:
The discovery of ether for the use as an anesthetic was in 1846 which marked the birth of a modern age in anesthesiology. The first true demonstration of ether as an inhalation anesthetic was on October 16, 1846 by William T.G. Morton, a Boston dentist. He discovered the anesthetic properties of ether in his search to provide patients with relief from painful dental procedures.
Preparation:
Advantages:
1. safe
2. does not modify blood pressure
3. economical
4. can be stored properly
Disadvantages:
1. induction of ether is slow
2. inflammable
3. recovery is slow.
Chloroform:
Chloroform or trichloromethane is an alkylchloride with the formula CHCl3. It is a very volatile, colorless, strong-smelling, dense liquid that serves as a powerful general anesthetic, and sedative.
Preparation:
Industrially, chloroform is produced by heating a mixture of chlorine and either methyl chloride (CH3Cl) or methane (CH4). At 400–500 °C, free radical halogenation occurs, converting these precursors to progressively more chlorinated compounds:
CH4 + Cl2 → CH3Cl + HCl
CH3Cl + Cl2 → CH2Cl2 + HCl
CH2Cl2 + Cl2 → CHCl3 + HCl
Disadvantages:
The anesthetic use of chloroform has been discontinued, because it caused deaths from respiratory failure and cardiac arrhythmias. Following chloroform-induced anesthesia, some patients suffered nausea, vomiting, , jaundice, and coma owing to hepatic dysfunction.
Chloroform converts slowly in the presence of UV light and air to the extremely poisonous gas, phosgene (COCl2), releasing HCl in the process.
2 CHCl3 + O2 → 2 COCl2 + 2 HCl
Tuesday, August 6, 2024
ARTIFICIAL SWEETENERS
Dear all,
We know about sugars and it gives sweet taste in our food stuffs. Sugars are used in our everyday life. There are wide variety of sugar brands we know. In this post we are going to discuss about sweeteners.
What are sugars?
Sugars are carbohydrates, found naturally in most plants. It is composed of carbon, hydrogen, and oxygen. All green plants make sugar through photosynthesis, the process plants use to transform the sun’s energy into food.
Where do we get sugars?
The most common sugar is sucrose in sugarcane and sugar beets.
malt syrup is derived by breaking down the starches in cooked rice.
Lactose is the naturally occurring form of sugar in milk products.
Fructose, a sugar found in fruits and honey.
What makes sugar sweet?
The sweetness of sugar comes from a chemical interaction between sugar molecules and sweet taste receptor cells, which are found in our taste buds of our tongue. Different types of sugars can have varying levels of sweetness. Fructose is the sweetest of all naturally occurring sugars.
Artificial Sweeteners:
Artificial sweeteners are chemically synthesized substances that are used instead of sucrose (natural sugar) to sweeten foods and beverages. They are many times sweeter than sugar and much smaller amounts (200 to 20,000 times less) are needed to create the same level of sweetness. The caloric content of sweeteners is very small, so it is described as nonnutritive.
It can be used directly in processed food such as puddings, dairy products, candy, soft drinks, baked goods, jams and many other foods and beverages.
Below is the list of some common artificial sweeteners commonly used.
1. Saccharin:
It was discovered in 1879 and is considered the oldest non-nutritive sweetener. It is about 300 times more sweet than sucrose, but it has a bitter aftertaste. It cannot be used in products where baking of food is necessary as it becomes unstable when it is heated. But it can be used to sweeten candies, drinks, and toothpaste.
Structure:
sodium ortho benzenesulphonamide |
2. Aspartame:
In 1879 Aspartame was discovered and it was found that it is approximately 200 times sweeter than sugar. It is commonly used as a tabletop sweetener and is also used in a variety of foods. When it is heated it breaks down into amino acids and loses its sweetness, so it cannot be used for baked foods. It is only used in soft drinks and cold foods.
3-amino-N-(α-carboxyphenethyl)succinamic acid N-methyl ester |
3. Cyclamate:
Cyclamate is an artificial sweetener and is about 30–50 times sweeter than sucrose (table sugar). It is the least potent of the commercially used artificial sweeteners. Hence, it is often used with other artificial sweeteners, especially saccharin. It is stable under heating.
cyclohexylsulfamate |
Advantages of Artificial Sweeteners
Weight Control:
If we want to lose weight, then we should use an artificial sweetening agent as virtually it carries zero calories. One gram of sugar carries 4 calories, and one teaspoon of sugar contains about 4 grams of sugar. So by eating 1 teaspoon also we gain 16 calories. So in the case of weight control, an artificial sweetening agent is the best option.
Diabetes:
It also helps in controlling diabetes as it does not raise the blood sugar levels because it does not contain the carbohydrates in it.
Thursday, August 1, 2024
COORDINATION POLYMERIZTION
Dear students,
This post is about polymerization using coordination complexes. Transition metal compounds along with group 13 halides are generally used as catalysts. The first catalyst of this type was Ziegler - Natta catalyst. Here the mechanism of this polymerization is discussed.
Coordination Polymerization by Jim Livingston on Scribd
LAWS OF THERMODYNAMICS
First law of thermodynamics: The first law of thermodynamics states that heat is a form of energy, and that heat energy cannot be created...
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Dear all, We know about sugars and it gives sweet taste in our food stuffs. Sugars are used in our everyday life. There are wide variety of...
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First law of thermodynamics: The first law of thermodynamics states that heat is a form of energy, and that heat energy cannot be created...
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Dear students, Here we are going to see about the next two antibiotics. Chloramphenicol Chloramphenicol is an antibiotic and is in the cla...