What is the Spin Quantum Number An electron orbiting around the nucleus has an intrinsic spin whose orientation is represented by the spin quantum number. Its value can determine the spin angular momentum along a specific axis using quantum theory [1-4]. According to Pauli Exclusion Principle, no two electrons can have the same set of… Continue reading Spin Quantum Number
Magnetic Quantum Number
We learned that the principal quantum number represents the energy of the electron shell, and the azimuthal quantum number represents the shape of the subshell. Let us study the third quantum number in the set. What is Magnetic Quantum Number The magnetic quantum number divides the subshell into orbitals and determines their number. Each value… Continue reading Magnetic Quantum Number
Azimuthal (Angular Momentum) Quantum Number
We learned that the principal quantum number represents the distance of the electron from the nucleus of an atom, and hence, the atomic size. Let us study the following quantum number in the set. What is Azimuthal Quantum Number Also known as the angular momentum quantum number or orbital quantum number, the azimuthal quantum number… Continue reading Azimuthal (Angular Momentum) Quantum Number
Principal Quantum Number
An atom consists of a nucleus surrounded by electrons in orbits or shells. A set of quantum numbers indicates the position and motion of the electrons. What is Principal Quantum Number The principal quantum number represents the distance of the electrons from the nucleus, and hence, the atomic size. It is denoted by the symbol… Continue reading Principal Quantum Number
Bohr Model
What is Bohr Model The Bohr model represents the structure of an atom developed by Danish physicist Niels Bohr in 1913. According to this model, the atomic structure is similar to that of the solar system. The nucleus represents the sun, and the electrons represent the planets orbiting around the nucleus. Unlike gravitational forces that… Continue reading Bohr Model
Electrophilic Addition
What is Electrophilic Addition (1-5) Electrophilic addition is a type of addition reaction where an electrophilic species combines with another compound to form a product without losing any atoms present in the reactants. As the name says, electrophiles are electron-loving species that accept electrons during the reaction. The pi bond (π bond) of unsaturated hydrocarbons… Continue reading Electrophilic Addition
Electron Shielding
What is Electron Shielding In a multi-electron atom, the orbiting electrons are attracted to the nucleus by electrostatic forces. However, due to the repulsive forces from the inner electrons, the outer electrons experience a reduced attractive force. In other words, the inner electrons shield the outer electrons from the nucleus. This phenomenon is known as… Continue reading Electron Shielding
Effective Nuclear Charge
An atom consists of the nucleus surrounded by electrons residing in different shells. Electrostatic forces of attraction arise between the nucleus and the electrons. Similarly, electrostatic repulsive forces also arise between the inner and the outer electrons. The repulsive forces weaken the attractive forces, resulting in electron shielding [1,2]. What is Effective Nuclear Charge According… Continue reading Effective Nuclear Charge
Quantum Numbers
What are Quantum Numbers Quantum numbers are a set of numbers used to define the state in which a fundamental particle like an atom, ion, nucleus, and electron resides. They represent the position, movement, and energy of the fundamental particle. For electrons, quantum numbers are significant since they designate the various discrete energy levels that… Continue reading Quantum Numbers
Pauli Exclusion Principle
What is Pauli Exclusion Principle The state in which an electron resides in an atomic orbital is designated by a set of four quantum numbers – principal quantum number (n), azimuthal quantum number (l), magnetic quantum number (ml), and spin quantum number (ms). Pauli exclusion principle states that no two electrons can have the same… Continue reading Pauli Exclusion Principle
Alkene Reactions
What is an Alkene Reaction? (1-4) Alkenes are hydrocarbons that contain one or more double bonds. Their double bond consists of a sigma (σ) bond and a pi (π) bond. The carbon-carbon π bond is formed by side-by-side overlapping. It is relatively weak and exhibits high reactivity. The bond can be easily broken, and reagents… Continue reading Alkene Reactions
Octet Rule
What is the Octet Rule Atoms are not stable by themselves. The octet rule states that the number of electrons in an atom’s outermost or valence shell must be eight to attain stability. During chemical bonding, atoms gain, lose, or share electrons and become stable. In an ionic bond, atoms transfer electrons and become ions.… Continue reading Octet Rule
Electrolysis
What is Electrolysis Electrolysis separates chemically bonded ionic substances and compounds by passing an electric current through them. It uses a direct current (DC) to drive a non-spontaneous reaction that occurs during the process [1-4]. English physicist Michael Faraday popularized electrolysis in the 19th century. How Does Electrolysis Work Electrolysis is carried out in an… Continue reading Electrolysis
Halogenation
What is Halogenation (1) Halogenation is a chemical reaction in which a halogen is added to a hydrocarbon by replacing one of its hydrogens. The product thus formed is known as a halogenated compound. It occurs in both saturated and unsaturated hydrocarbons and aromatic hydrocarbons. The most common halogens in this reaction are fluorine, chlorine,… Continue reading Halogenation
Hydrohalogenation
What is Hydrohalogenation (2) Hydrohalogenation is a type of electrophilic addition reaction that occurs in unsaturated compounds like alkene and alkyne. A hydrogen halide (HX), such as hydrogen chloride (HCl) or hydrogen bromide (HBr), adds to an alkene, producing the corresponding haloalkanes or alkyl halides. The reaction is carefully carried out in the presence of… Continue reading Hydrohalogenation
Excess Reagent
What is an Excess Reagent (1-5) Excess reagent is the reactant or reagent that is left after a chemical reaction is complete. In other words, when a chemical reaction takes place, a reactant remains present in greater quantity than required to complete the reaction. It is not entirely consumed during a reaction. Because of its… Continue reading Excess Reagent
Catalytic Reaction (Catalysis)
What is a Catalytic Reaction [2,4-6] Catalysis is the process that alters the rate of a chemical reaction under the influence of a catalyst. A catalyst is a chemical substance added to a reaction to either accelerate or decelerate the reaction rate without itself undergoing any change. Characteristics of Catalytic Reaction [6] The catalyst remains… Continue reading Catalytic Reaction (Catalysis)
Aufbau Principle
An atom consists of a nucleus around which electrons revolve in well-defined orbits. The orbits are characterized by sublevels or subshells, which are organized according to their increasing energies. What is Aufbau Principle The construction of a model of an atom begins by filling up the electrons in the lowest energy subshell. Aufbau principle gives… Continue reading Aufbau Principle
Lewis Structure
What is Lewis Structure Lewis structure, also known as Lewis dot structure or electron dot structure, is a simple and straightforward way of representing the outermost electron shell in a chemical species like an atom, ion, or molecule. It shows how electrons are positioned around the atoms either as lone pairs or in a chemical… Continue reading Lewis Structure
Elementary Reaction
What is an Elementary Reaction [1-2] An elementary reaction is a chemical reaction where reactants directly form products in a single step with a single transition state. Here, no intermediate products are formed. The transition state is the phase of the reaction where the reaction attains the highest energy. It is a very short-lived stage,… Continue reading Elementary Reaction
Formal Charge
What is a Formal Charge [1-8] A formal charge is a charge assigned to an atom in a molecule, assuming that all electrons in the chemical bonds are shared equally between the atoms. This assumption excludes the electronegativity difference between the atoms. The sum of formal charges of all the atoms is equal to the… Continue reading Formal Charge
Buffer Solution
What is a Buffer Solution [1-3,5-6] An aqueous solution that resists any change in pH by adding a small amount of acid or base is called a buffer solution. A buffer solution consists of a weak acid and its conjugate base or a weak base and its conjugate acid. A buffer solution can resist pH… Continue reading Buffer Solution
Metathesis Reaction
What is Metathesis Reaction [1-12] Metathesis reaction is the exchange of atoms or functional groups in substrates and the rearrangement of their matching partners (substituents) to form new compounds. Also known as exchange reaction, metathesis is a bimolecular process resulting in products with similar bonding. Types and Examples of Metathesis Reaction [1-10] 1. Olefin (Alkene)… Continue reading Metathesis Reaction
Dynamic Equilibrium
What is Dynamic Equilibrium [1-4] Equilibrium refers to the steady-state in a chemical reaction, where the reactant’s concentration is equal to the product’s concentration. Dynamic equilibrium can be defined as the steady state of a reversible reaction occurring in a closed system. Both the forward and reverse reaction proceeds in the opposite direction with equal… Continue reading Dynamic Equilibrium
Limiting Reagent (Reactant)
What is Limiting Reagent [1 – 4] A limiting reagent or limiting reactant is a substance that has been wholly consumed in a chemical reaction. Thus, the limiting reagent determines when to complete and stop a reaction. Since the limiting reagent is consumed in a reaction, no amount remains to react with another reactant. Therefore,… Continue reading Limiting Reagent (Reactant)
Hund’s Rule
What is Hund’s Rule[1-4] An atom consists of a nucleus around which electrons revolve in well-defined orbits. The electrons reside in orbitals of sublevels of different energy. According to the Aufbau principle, electrons fill the lowest energy sublevel before filling up the higher ones. Thus, electrons are found in discrete atomic sublevels in an arrangement… Continue reading Hund’s Rule
Autoionization (Self-ionization) of Water
The autoionization or self-ionization of water is an endothermic ionization reaction where a molecule of pure water gets dissociated into hydrogen ions (H+) and hydroxyl ions (OH-). As water is a very weak electrolyte, it gets ionized minimally. Autoionization Chemical Equation When two water molecules collide, a hydrogen ion from one molecule gets transferred to… Continue reading Autoionization (Self-ionization) of Water
Chemical Equilibrium
What is Chemical Equilibrium Chemical equilibrium is the condition of a system where the concentrations of the reactants and products do not change with time. Also, the system does not show any change in its properties. During a reversible reaction, when the forward and reverse reaction rates become equal, the system achieves the state of… Continue reading Chemical Equilibrium
Henderson-Hasselbalch Equation
The Henderson-Hasselbalch equation is an equation used in chemistry and biochemistry to determine the pH value of a buffer solution during the dissociation of a weak acid. A weak acid does not dissociate completely. A property of the buffer solution is that the mixture can resist changes in pH when a small amount of acid… Continue reading Henderson-Hasselbalch Equation
Saponification
What is Saponification The process of converting fats, oil, and lipid into soap using an aqueous alkali is called saponification. Vegetable oil and animal fats are triesters or triglycerides that can be saponified in one or two steps. During this process, the triglyceride reacts with an aqueous hydroxide ion to form a mixture of glycerol… Continue reading Saponification
E2 Reaction
What is E2 Reaction E2 reaction is a type of elimination reaction. A beta-hydrogen and a leaving group are removed from a compound (substrate) to form a double bond in a single concerted step. The removal usually takes place in the presence of a strong base that removes the proton. The rate of reaction is… Continue reading E2 Reaction
E1 Reaction
What is E1 Reaction? E1 reaction is a type of elimination reaction in organic compounds. A beta-hydrogen and a leaving group attached to two adjacent carbon atoms are removed from a compound (substrate) to form a double bond. The removal usually occurs in two steps in the presence of a Lewis base or acid, resulting… Continue reading E1 Reaction
Nucleophilic Addition
What is Nucleophilic Addition? A nucleophile addition is an addition reaction in which a nucleophile adds to a pi bond of a compound. As a result, two new sigma bonds are formed. This reaction is essential in organic chemistry because it enables carbonyl compounds to form new products having various functional groups. Carbonyl compounds undergo… Continue reading Nucleophilic Addition
Nucleophilic Acyl Substitution
What is Nucleophilic Acyl Substitution? Nucleophiles are electron-rich species that are capable of donating electrons to an electrophile. They have a lone pair of electrons that attack electron-deficient sites in a molecule, thereby forming a new bond. Nucleophilic acyl substitution is a substitution reaction in which a nucleophile displaces a leaving group (LG) bonded to… Continue reading Nucleophilic Acyl Substitution
Nucleophilic Aromatic Substitution
What is Nucleophilic Aromatic Substitution? Nucleophilic aromatic substitution is a nucleophilic substitution reaction in which a nucleophile displaces a leaving group bonded to the carbon ring of an aromatic compound. In this reaction, a nucleophile attacks an aromatic ring that is deficient in electrons. The presence of an electron-withdrawing group facilitates the reaction. A typical… Continue reading Nucleophilic Aromatic Substitution
Nucleophile
What is a Nucleophile A nucleophile is a reagent consisting of an atom, ion, or molecule that donates electron pair to form a bond. It is an electron-rich species that can be negatively charged or neutral with available electrons. A nucleophile reacts with an electrophile by donating electrons to form the bond [1-5].
Electrophile
What is an Electrophile An electrophile is a reagent consisting of an atom, ion, or molecule that accepts electron pair to form a bond. It is an electron-deficient species that can be positively charged or neutral with vacant orbitals. An electrophile reacts with a nucleophile by accepting electrons through addition and substitution reactions.
Brønsted-Lowry Theory
What is the Brønsted-Lowry Theory? The Brønsted–Lowry theory describes the interaction between an acid and a base in terms of proton transfer. According to this theory, a substance can function as an acid only in the presence of a base. Similarly, a substance can function as a base only in the presence of an acid.… Continue reading Brønsted-Lowry Theory
Hell-Volhard-Zelinsky Reaction
Explanation: What is Hell-Volhard-Zelinsky Reaction? The Hell-Volhard-Zelinsky (HVZ) reaction is an organic reaction that is used to convert a carboxylic acid consisting of alpha hydrogen to an α-halo carboxylic acid, using a phosphorous catalyst, halogen gas, and water. It is a type of substitution reaction. Typically, red phosphorus and bromine are treated with the carboxylic… Continue reading Hell-Volhard-Zelinsky Reaction
Rosenmund Reduction
Definition: What is Rosenmund Reduction? Rosenmund Reduction is an organic chemical reaction in which an acid chloride is converted to an aldehyde by using hydrogen gas passed over palladium (Pd) on barium sulfate (BaSO4). Barium sulfate reduces the activity of palladium due to its low surface area. As a result, it decreases the reducing power… Continue reading Rosenmund Reduction
Perkin Reaction
Definition: What is Perkin Reaction? The Perkin reaction, also known as Perkin condensation, is an organic reaction which is used for the synthesis of α,β-unsaturated aromatic acid by the condensation of an aromatic aldehyde and an acid anhydride, in the presence of an alkali salt of the acid acting as a weak base. Generally, such… Continue reading Perkin Reaction
Balz-Schiemann Reaction
Definition: What is Balz Schiemann Reaction? The Balz–Schiemann reaction is a chemical reaction in which a primary aromatic amine is transformed into an aryl fluoride via diazonium tetrafluoroborate intermediate. The primary reactants are aryl amines, nitrous acid, and fluoroboric acid. The process involves the conversion of arylamines to aryl fluorides via diazotization and subsequent thermal… Continue reading Balz-Schiemann Reaction
Bredt’s Rule
What is Bredt’s Rule? Bredt’s rule is an empirical observation in organic chemistry that states that a double bond cannot be placed at the bridgehead of a bridged ring system unless one of the rings is big. A bridgehead is an atom that is part of two or more rings in a polycyclic molecule. In… Continue reading Bredt’s Rule
Collins Reagent
Definition: What is Collins Reagent? Collins reagent is the complex of chromium (VI) oxide with pyridine in dichloromethane. It is a red-colored metal-pyridine complex and is used to oxidize primary alcohols to aldehyde without overoxidation. Its molecular formula is C10H10CrN2O3. It is useful for oxidizing acid-sensitive compounds, and the process is known as Collins oxidation.… Continue reading Collins Reagent
Walden Inversion
Definition: What is Walden Inversion? The inversion of configuration at a chiral center during a bimolecular nucleophilic substitution (SN2 reaction) is generally known as the Walden inversion. Since the molecule can form two enantiomers around the chiral center, Walden inversion transforms the structure of the molecule from one enantiomeric form to another. Walter inversion has… Continue reading Walden Inversion
Baeyer’s Reagent
Definition: What is Baeyer’s Reagent? Baeyer’s reagent is an alkaline solution of cold potassium permanganate (KMnO4). It is a potent oxidizing agent and is used in qualitative organic analysis to test for the presence of unsaturation. This solution interacts with an unsaturated compound (e.g., alkene or alkyne), changing its pinkish-purple color to brown. The alkene… Continue reading Baeyer’s Reagent
Barfoed’s Test
Definition: What is Barfoed’s Test? Barfoed’s test is a chemical test used for detecting the presence of monosaccharides. It is based on the reduction of cupric (II) acetate to cuprous (I) oxide (Cu2O), which forms a brick-red precipitate. Disaccharides may react, but the reaction is much slower because they have to get hydrolyzed first and… Continue reading Barfoed’s Test
Haworth Projection
Definition: What is Haworth Projection? Haworth projection is a common way of writing a structural formula of sugars (monosaccharides and disaccharides) with an unpretentious three-dimensional perspective. This type of illustration is mostly used in organic chemistry, especially biochemistry. Haworth projection differs from Fischer projection in that it represents the carbohydrate in its cyclical form. It… Continue reading Haworth Projection
Fischer Projection
Definition: What is Fischer Projection? Fischer projections are best used to represent the straight-chain structures of monosaccharides and some amino acids. They represent structural forms that allow one to convey valuable stereochemical information by drawing 3D molecules as flat structures. An advantage of such structures is that they can easily represent multiple stereocenters, and allow… Continue reading Fischer Projection
Substitution Reaction
Definition: What is a Substitution Reaction? A substitution reaction is an organic chemical reaction during which a functional group replaces an atom or another functional group attached to a carbon atom in a compound.
Mitsunobu Reaction
Definition: What is Mitsunobu Reaction? The Mitsunobu reaction is a common SN2 reaction taking advantage of phosphorous chemistry. It is an organic reaction that converts primary or secondary alcohol into a variety of functional groups (e.g., ester) using triphenylphosphine and an azodicarboxylate such as diethyl azodicarboxylate (DEAD) or diisopropyl azodicarboxylate (DIAD). The alcohol reacts with… Continue reading Mitsunobu Reaction
Cannizzaro Reaction
Definition: What is Cannizzaro Reaction? Cannizzaro reaction is an organic reaction of an aldehyde without active hydrogen that undergoes a redox reaction under the action of a strong base. Examples of aldehydes without active hydrogen include vanillin, benzaldehyde, syringaldehyde, and formaldehyde. They undergo intramolecular and intermolecular oxidation-reduction reactions under the action of a strong base… Continue reading Cannizzaro Reaction