Category: Chemistry Notes PPT

Ammonia is a pungent and colorless substance, which is composed of nitrogen and hydrogen. It is one of the simplest stable compounds of these elements, and it serves as a starting material for the formation of several commercially essential nitrogen compounds.

The chemical formula of ammonia is given as NH3.

Structure

The ammonia molecule contains a trigonal pyramidal shape, which is predicted by the VSEPR theory – Valence Shell Electron Pair Repulsion with an experimentally described bond angle of 106.7°. The central nitrogen atom contains 5 outer electrons, including an additional electron from every hydrogen atom. This gives a complete set of four electron pairs of eight electrons that are arranged tetrahedrally. Three of these electron pairs are used as bond pairs, which leave a single lone pair of electrons.

The lone pair repel more strongly compared to the bond pairs; thus, the bond angle is not as expected, 109.5°, for a regular tetrahedral arrangement, but it is 106.7°. This specific shape gives the molecule a dipole moment and makes it polar.

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Industrial Production of Ammonia

Industrially, the global production of ammonia in 2018 was listed as 175 million tonnes, with zero significant change relative to 2013’s global industrial production, which is given as 175 million tonnes. Industrial ammonia is sold either in the form of ammonia liquor (generally 28% of ammonia in water) or as refrigerated or pressurized anhydrous liquid ammonia, which is transported in cylinders or tank cars.

NH3 boils at a temperature of −33.34 °C  and at a pressure of one atmosphere, and because of that, the liquid should be stored at low temperature or under pressure. hydroxide or Household ammonia is a solution of NH3 in water. Such concentrated solutions are measured in the Baumé scale units (density), with 26 degrees of Baumé (by weight – about 30% ammonia at 59.9 °F or 15.5 °C) being a typical high-concentration commercial product.

Etymology

Pliny, in a book, refers to a salt produced in the Roman province of Cyrenaica named hammoniacum, so-called due to its proximity to the nearby Temple of Jupiter Amun. However, the description given by Pliny on salt does not conform to the ammonium chloride properties. According to the commentary of Herbert Hoover in his English translation of Georgius Agricola’s De re Metallica, it is more likely to have been common sea salt. Ultimately, in any case, that salt gave ammonium and ammonia compounds their name.

Natural Occurrence

Ammonia can be found chemically in trace quantities in nature, being formed from nitrogenous vegetable and animal matter. Both ammonium and ammonia salts are also found in the fewer quantities in rainwater, whereas ammonium sulfate and ammonium chloride (sal ammoniac) are found in volcanic districts; ammonium bicarbonate crystals have been found in the Patagonia guano. The kidneys secrete ammonia in excess acid neutralization. Ammonium salts can also be found distributed in seawater and through fertile soil.

Amphotericity

The most characteristic properties of ammonia are given as its basicity and is considered to be a weak base. It also combines with acids to produce salts; hence with hydrochloric acid, it forms ammonium chloride, ammonium nitrate, nitric acid, etc. Perfectly dry ammonia will not always combine with perfectly dry hydrogen chloride. Moisture is required to bring about the reaction. Opened bottles of the concentrated hydrochloric and ammonia acid produce clouds of ammonium chloride as a demonstration experiment, which seems to appear “out of nothing” because the salt produces where the two diffusing clouds of molecules meet, at some point between the two bottles.

NH3 + HCl → NH4Cl

The salts, which are produced by the ammonia action on acids, are called ammonium salts, and all contain ammonium ion (NH4+).

Formation of Other Compounds

In organic chemistry, ammonia acts as a nucleophile in substitution reactions. Amines are formed by the ammonia with alkyl halide reaction, although the resulting -NH₂ group is nucleophilic, and the secondary, tertiary amines are often resulting as byproducts. An ammonia excess helps to minimize the multiple substitutions and neutralizes the formed hydrogen halide. 

Methylamine can be commercially prepared by the ammonia with chloromethane reaction, and the ammonia with 2-bromopropanoic acid reaction has been used to prepare the racemic alanine in the yield of 70%. Ethanolamine can be prepared by a ring-opening reaction with ethylene oxide, which sometimes, the reaction is allowed to proceed further to form “di” and triethanolamine.

Ammonia as a Ligand

Ammonia acts as a ligand in the transition metal complexes. In the middle of the spectrochemical series, it is a pure σ-donor and exhibits intermediate hard-soft behavior. The relative donor strength of this acid toward a series of acids versus other Lewis bases can be illustrated by the C-B plots. For historical reasons, ammonia is named as ammine in the coordination compound’s nomenclature.

A few notable ammine complexes are given as tetraamminediaquacopper (II), with the chemical formula [Cu(NH3)4(H2O)2]2+), which is a dark blue complex formed by adding ammonia to a copper(II) salt solution.

What do Antibiotics do?

Antibiotics are a group of powerful medicines which fight against infections and can also save our lives when we use them correctly. They work either by stopping the bacterial reproduction or by destroying them completely. However, before bacteria are multiplied and cause symptoms, our immune system kills them. The white blood cells attack the harmful bacteria and even though it causes symptoms, our immune system can usually cope and fight with the infection. However, sometimes, when the harmful bacteria are excessive in number and our immune system cannot fight them, antibiotics are used.

If you know what is penicillin, you would know that it was the first-ever antibiotic to be discovered. There are several penicillin-based antibiotics like amoxicillin, ampicillin, and penicillin G, which are used even today in the treatment of several infections. There are many topical antibiotics available as well in the form of OTC ointments and creams.

Today we will discuss what are antibiotics, what do antibiotics do, what are antibiotics used for, and how long do antibiotics take to work.

Antibiotics Definition

Let us now discuss the antibiotic meaning and its definition.

Antibiotics are defined as a type of an antimicrobial drug that is used for treating and preventing bacterial infections through the inhibition of the growth of bacteria. Antibiotics are not effective on the diseases that are caused due to viruses, like flu or cold.

History of Antibiotics

Let us discuss the penicillin meaning, penicillin history, how penicillin work, and take a look at what penicillin is used for.

Initially, the antibiotics were obtained from microorganisms. In the later years after the advancement of synthetic methods, antibiotics were developed synthetically.

In the nineteenth century, a German bacteriologist, Paul Ehrlich, started to look for a chemical which could kill bacteria in both the bodies of humans as well as animals, but which does not affect their health. After conducting several types of research, he discovered a medicine called arsphenamine, which is also called salvarsan. It was used in the treatment of syphilis, caused by the bacteria spirochete. He received a Nobel Prize for the same in the year 1908. Though this medicine had some side effects, its impact on the bacteria was so much more than on the humans.

In the year 1932, another drug known as prontosil was discovered by the group of researchers located at Bayer Laboratories. This was much similar to salvarsan that tends to convert into sulphanilamide when taken into the body.

However, the actual transformation in regards to the antibacterial therapy happened with the discovery which was made by Alexander Fleming in the year 1929, of the naturally developed antibiotic called penicillin.

How do Antibiotics Work?

Although there are many different kinds of antibiotics, they tend to work in two basic ways.

1. Certain antibiotics like penicillin tend to get rid of the bacteria when they kill it. They usually do so by disrupting the formation of the cell content or the cell wall of the bacteria.

2. The other kind of antibiotics tends to inhibit the multiplication action of the bacteria.

Types of Antibiotics

Antibiotics are typically classified depending on their chemical structure. Antibiotics having the same structural class have similar properties when it comes to effectiveness, allergy potential, and toxicity. They are:

1. Penicillins

2. Macrolides

3. Sulfonamides

4. Cephalosporin

5. Tetracyclines

6. Fluoroquinolones

7. Aminoglycosides

Depending on how they work to stop the bacterial infection, they are classified as follows:

• Bactericidal: They tend to kill the bacteria that is present in the body that causes diseases. Examples include penicillin, polymyxin, etc.

• Bacteriostatic: They are the medicines that are used for inhibiting microbial growth. The examples include Chloramphenicol, Tetracycline, etc.

Depending on the range of action of antibiotics, they are classified as follows:

These are the drugs which inhibit or destroy the growth of a huge range of both the gram-positive and the gram-negative bacteria. For e.g;  Amoxicillin

These types of antibiotics typically attack Gram-positive bacteria or gram-negative bacteria. For e.g; Penicillin G

These antibiotics are effective against a particular type of organism or even a disease.

What is Antibiotic Resistance?

The emergence of bacterial resistance to antibiotics is quite a common phenomenon. The emergence of bacterial resistance tends to often reflect on the evolutionary processes which take place during the time of the antibiotics therapy. The treatment of antibiotics might tend to select for the bacterial strains having genetically or physiologically enhanced capacity for surviving higher doses of the antibiotic medication. Under a few conditions, it can result in a preferential resistant bacterial growth, whereas the susceptible bacterial growth gets inhibited by the antibiotic.

Arginine or L-arginine is an amino acid that is obtained by the hydrolysis of several common proteins, but specifically proteins associated with histones and protamines as they are associated with nucleic acids. The amino acid was first isolated in 1895 from an animal horn, and since then, extensive studies have shown its importance in living organisms. Arginine plays a critical role in all mammals for the synthesis of urea, it is the form in which mammals excrete nitrogen from their body. It is one of the many nonessential amino acids found in adult mammals.

Basic Introduction of Arginine

Arginine is synthesized in these species from glutamic acid without the supplement of any additional dietary sources. It is also found in poultry, red meat, fish, and other dairy products. Upon further studies, it is found that arginine also stimulates the release of insulin, growth hormone, and other important substances in the body. It breaks down during a chemical reaction and is converted into nitric oxide, which causes the blood vessels to open up broader for better blood circulation. 

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Uses of Arginine

Due to this exceeding importance, arginine supplements are used for various medical treatments. Heart and blood vessel medical conditions like congestive heart failure, high blood pressure, chest pain, and coronary artery disease are treated with the help of arginine. 

It is also used to treat the recurrent pain in the legs, which is caused due to blocked arteries, erectile dysfunction, decreased mental capacity usually found in elderly people, and male infertility. Doctors also use arginine supplement to treat and improve kidney function after kidney transplant surgery is performed. The kidney is particularly vulnerable and needs an extra boost to settle in and function in the new body. 

Arginine also prevents the common cold and greatly improves the athletic performance of an individual. Furthermore, arginine can also be used to boost the immunity of a person and prevent digestive tract inflammation in premature individuals. Naturally, it can be concluded that L-Arginine is vital for the growth of T-cells, which are also known as white blood cells, and they play an important role in the immune response. As these amino acids play such a critical role, the lack of them in the body will disrupt organ and cellular function, leading to serious health complications.

Benefits of L-Arginine Supplements

Some of the benefits and uses of the L-Arginine supplement were briefly mentioned above. Below given is more information on the same and additional benefits of arginine amino acid.

1. Regulation of Blood Pressure

Scientific studies have shown that by taking L-arginine supplements, one can lower one diastolic and systolic blood pressure. As mentioned above, L-arginine is important for the production of nitric oxide, which is required for the blood vessels to relax. Thus regulates the blood pressure in the human body.

2. Treating Erectile Dysfunction

A 2019 review of a total of 10 studies found that taking L-arginine supplements in 1.5-5 grams of daily dosage range can considerably improve erectile dysfunction as compared to other or no treatment.

3. Preventing and Treating Preeclampsia

Preeclampsia is a dangerous blood pressure condition found in women during pregnancy. It is also characterized by high levels of protein in their urine. Studies have proven that intake of arginine in regulated dosages can treat and possibly prevent preeclampsia in pregnant women.

4. Managing Critical illness

Infections and trauma drastically affect your body and make it vulnerable. Therefore, the Arginine need in your body considerably increases because of physiologic demands. When the body cannot internally meet arginine demands, it needs to be fulfilled externally. Oral or IV arginine amino acid is usually administered to treat grave infections, such as necrotizing enterocolitis in babies, chronic diseases, sepsis, serious wounds, and burns.

Enhancement of Athletic Performance

Although the evidence is limited, it suggests that arginine supplements can improve the exercise capacity by elevating nitric oxide in the human body, enhancing blood circulation and oxygenation to the muscles. However, the intake of L-arginine to enhance athletic performance is controversial as many studies have shown that arginine supplements are not beneficial for the same.

Aspartic acid is an acidic amino acid with functional groups of two carboxylic groups along with one amino group. There are about 20 important types of amino acids that are found in nature, more on this later. Every amino acid molecule is made up of two functional groups, they are opposite in characteristics, one is an amino group, and then there is a carboxylic acid. An aspartic acid structure is no exception; it contains one α-amino group which is in NH3+ forms and the carboxylic group that is in deprotonated –COO-. The aspartic acid formula looks like this- (C4H7NO4). Aspartic acid is a non-essential amino acid as the human body can synthesize it as it is needed.  Aspartic acid can be found in a plethora of eatables including oysters, avocado, sugar beets etc.

Why Is Aspartic Acid Different From Other Amino Acids?

As we previously discussed that amino acid has two functional groups, here we will dive a little deeper and shine some light on the third group, the R-group or the side chains, that gives the aspartic acid structure a distinction from the other amino acids such as glycine or cysteine. The R-group of the amino acids exerts profound changes in the biological activity of proteins. Amino acids are generally classified based on the characteristics of the functional group on the side chain in a neutral pH medium. They can be polar or nonpolar, polar yet charged, negatively charged or positively charged. The carboxyl group that is present in the side chain of the aspartic acid structure is ionized at physiological pH, which is known as aspartate, it is also from where the acid gets its name from. Glutamic acid also shares this sub-category with aspartic acid, the ionized carboxyl group in Glutamic Acid is known as glutamate.

Aspartic acid is a non-essential amino acid; it plays a vital part in the synthesis of amino acids and the citric acid and urea cycles. Aspartic acid commonly occurs in its L-form. It is found in plants and animals, especially in sugar beets and sugar cane. Here is a quick table consisting of the sources of this acid

Sources Of Aspartic Acid

Aspartic Acid Structure And Types Of Aspartic Acid      

Aspartic acid is a dicarboxylic amino acid that means it is an acidic polar α-amino acid with two carboxylic groups and one of the carboxyl groups is attached with one additional methylene group. Aspartic acid has the isoelectric point of 2.77, because of these two carboxylic groups. It is also called ‘succinic acid’. The presence of the second carboxyl group makes it very hydrophilic, it has pKA of 3.85, and this group can also form an ionic bond with almost any metallic ion and also participate in a dipole interaction with water. As an aspartic acid molecule is negatively charged in neutral pH, it can be found at the surface of proteins. The carboxyl group bonded on alpha-carbon has a pKa value of 1.88; -COOH group at the side chain has the value of 3.65 and 9.60 for the amino group. The aspartic acid formula is C4H7NO4,  and the aspartic acid structure looks like this –

There are two enantiomers of the aspartic Acid, namely- L-aspartic Acid, D-aspartic Acid. There is not much difference between these two. The first one is directly incorporated into proteins, but D-aspartic acids are more limited. Enzymatic synthesis can produce either of these acids.

Aspartic Acid Hybridization

• The molecular aspartic acid formula is HOOCCH(NH2)CH2COOH and has the molecular weight of 133.1g/mol.

• Aspartic acid has the IUPAC name- 2-Aminobutanoic acid.

• The atoms that are inside part of the aspartic acid have sp2 hybridization.

• The nitrogen atom is touching three other atoms, i.e. one carbon and two hydrogen atoms. It is sp3 hybridized.

• C1 and C4 are sp2 hybridized with trigonal planar geometry with 120o angle. The other two carbon atoms, i.e. C2 and C3, are sp3 hybridized with tetrahedral geometry in a 109o bond angle.

• The carbon atoms in the carboxyl groups are sp2 hybridized.

Examples

1. What Type of Acid is Aspartic Acid?

Answer: Aspartic acid is a non-essential acidic amino acid.

2. What is The Aspartic Acid Formula and Its Molecular Weight?  

Answer: The chemical formula of aspartic acid is C4H7NO4 and its molecular weight is 133.1g/mol. 

3. What Are The Two Functional Components of Aspartic Acid? 

Answer: The two functional components of aspartic acid are one amino group and two carboxyl groups. 

4. What Are The Two Types of Aspartic Acid? 

Answer: There are two types of aspartic acid i.e. L-aspartic acid and D-aspartic acid. 

Did You Know

The aspartic Amino acid is a non-essential amino acid; in mammals, the synthesis of this amino acid is self-regulatory through the central metabolism pathway. You won’t be out of breath after running four yards if you eat oysters and avocados more since it has a significant level of aspartic amino acid. Amino acids are the building blocks for the proteins in your body.    

Aufbau is a German word that means ‘building up and is not the name of a scientist unlike many of the other principles of chemistry. This principle is concerned with the filling of the electrons in an orbital during the writing of an electronic configuration.

‘Building up’, as the name suggests, is regarding the filling of the orbitals with electrons to build the electronic configuration in a particular way so that an orbital with lower energy is filled earlier and the orbital with higher energy is filled later.

In other words, “In a ground state of the atoms, the orbitals are filled in order of their increasing energies.” i.e. an electron will initially occupy an orbital of lower energy level and when the lower energy level orbitals are occupied, then only they shall start occupying the higher energy level orbitals.

 

Salient Features of the Aufbau Principle

The energy of an orbital is determined by the (n+l) rule where ‘n’ stands for the Principal quantum number and ‘l’ stands for the Azimuthal quantum number. The lower the value of (n+l) for an orbital, the lower will be its energy. And, if two orbitals have the same value for (n+l) then the one with a higher value of n will have higher energy.

During filling up of electrons in the orbitals for completion of electronic configuration, electrons will first occupy the orbitals of lower energy; only after the lower energy orbitals are occupied, the electrons shall occupy the higher energy orbitals.

The order in which the energies of the electronic orbitals increase and their respective order of filling as per the Aufbau rule is as follows:

Figure 1. Order of filing of orbitals by Aufbau principle

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 4f, 5d, 6p, 7s…

This diagram is also referred to as the Aufbau principle diagram and is used to remember the order of the filling of the orbitals.

In a tabular form, the arrangement of orbitals with increasing energies as per The electronic(n+l) rule can be shown as follows:

 

Note: Values of Azimuthal quantum numbers are as follows: s=0, p=1, d=2, f=3.

 

Electronic Configuration using the Aufbau Principle

According to the Aufbau rule:

First electrons are filled in 1s orbital. Since each orbital can accommodate a maximum of only 2 electrons so 1s orbital contains 2 electrons. Then 2s orbital is filled as it is the one that comes after 1s in terms of energy level. This also can accommodate 2 electrons. Then, electrons are filled in the 2p atomic orbitals: 2px which are can accommodate 2 electrons, 2py which can accommodate 2 electrons, and 2pz which can accommodate 2 electrons. Since px, py, and Pz are degenerate orbitals, so their energy levels are also the same. So, the electrons can occupy either of the 3 in any order. Thus, 2p can accommodate a total of 6 electrons. Then, electrons are filled in the 3s orbital which can accommodate a total of 2 electrons, followed by the filling of the 3p orbitals similar to 2p orbitals and so on.

The filling of the orbitals goes on according to the Aufbau rule/Aufbau principle. However, the location, the order of the filling of electrons according to their spin while filling in the degenerate orbitals, and the spin of the 2 electrons filled in the same orbital itself are further basically governed by Hund’s rule and Pauli’s exclusion principle. 

 

Writing the Electronic Configuration of Sulfur

Sulfur has an atomic number of 16 i.e., it has 16 electrons in an atom. As stated above, the first 2 electrons will be occupied by the 1s orbital. The next 2 will be occupied by the 2s orbital. The next 6 electrons will be occupied by the 2p orbitals. The next 2 electrons will be occupied by the 3s orbital and the rest of the final 4 electrons will be occupied by the 3p orbitals. So, out of the 16 electrons, a total of 10 electrons lie in the 1st and the 2nd shell i.e. n=1 and n=2 and the last 6 electrons lie in the 3rd shell i.e. n=3. So, the valence shell is the 3rd shell, and the total number of valence electrons is 6 (2 electrons in 3s and 4 electrons in 3p) in sulfur. We filled electrons according to the Aufbau principle and used figure 1. 

The electronic configuration is written in the following fashion:

S = 16; Electronic configuration as per Aufbau rule: 1s2,2s2,2p6,3s2,3p4.

Writing the Electronic Configuration of Nitrogen

The electronic configuration of nitrogen is written similarly just like that of sulfur. Nitrogen has an atomic number of 7 i.e., it has 7 electrons in total. The first two electrons are occupied by the 1s orbital. The next 2 electrons lie in the 2s orbital and the last 3 electrons lie in the 2p orbitals. 

Therefore, the 1st shell has 2 electrons, and the 2nd shell has 5 electrons. So, the valence shell is the 2nd shell i.e. n=2 and the number of valence electrons are 5 (2 electrons in 2s and 3 electrons in 2p).

The electronic configuration is written in the following fashion:

N = 7; Electronic configuration as per Aufbau rule: 1s2,2s2,2p3.

Even though most of the electronic configurations follow the above order as stated in the Aufbau principle, there are certain exceptions. A handful of elements with atomic number greater than 20, such as Cu (Copper, atomic number = 29), Cr (Chromium, atomic number = 24, Mo (Molybdenum, atomic number = 42), etc., are exceptions. These exceptions arise becau
se filled or half-filled atomic orbitals are more stable than any of the partially filled atomic orbitals because of symmetry and the release of exchange energy.

Paulis Exclusion Principle

According to the Pauli exclusion principle, no two electrons in a single atom will have an identical set or the same quantum numbers. Every electron should have or be in a distinct state. Pauli’s Exclusion Principle essentially helps us comprehend the electron configurations in atoms and molecules and also explains the periodic table’s classification of elements. The Pauli Exclusion Principle adheres to two major principles:

• Only two electrons can occupy the same orbital.

• The two electrons that are present in the same orbital must have opposite spins or they should be antiparallel.

Pauli’s Exclusion Principle, on the other hand, does not only apply to electrons. It also applies to fermions and other particles with half-integer spin. It is significant for particles with integer spins, such as bosons, which have symmetric wave functions. Moreover, unlike fermions, bosons can share or have the same quantum states. Fermions are called after the Fermi–Dirac statistical distribution that they follow in terms of nomenclature. The Bose-Einstein distribution function, on the other hand, is where bosons derive their name.

Hund’s Rule

According to Hund’s rule, a larger total spin state of an atom can occasionally make the atom more stable. This rule is fairly reliable (with a few exceptions) for determining the state of a given excited electron configuration. Friedrich Hund found it in the year 1925. According to Hund’s rule:

Because an electron can fill all of its orbitals with identical energy, it will not couple with another electron in a half-filled orbital. Atoms in their ground state contain a large number of unpaired electrons. When two electrons come into contact, they react in the same way as two magnets do. Before they have to couple up, the electrons want to go as far apart from each other as possible. Hund’s Rule can assist anticipate atomic characteristics since paired and unpaired electrons have different properties (specifically with interactions with magnetic fields).