Regioselectivity refers to the preference of a chemical reaction to occur at one specific location over another in a molecule that contains multiple reactive sites. This selectivity is particularly significant in organic chemistry, where a molecule may have several functional groups or double bonds that can potentially react. For example, in the case of electrophilic addition reactions or substitutions, a reagent might attack different positions on a substrate. Regioselectivity indicates which position the reagent preferentially reacts with, leading to a major product.

Specific rotation is a physical property of optically active substances that measures the degree to which a compound can rotate the plane of polarized light. It is particularly important in the study of chiral molecules, such as many organic compounds and certain biomolecules.

The staggered conformation is a specific arrangement of atoms in a molecule, particularly relevant in the context of organic chemistry and the study of alkanes. In a staggered conformation, the substituents or groups attached to adjacent carbon atoms are positioned as far apart from each other as possible. This arrangement minimizes steric strain and torsional strain between the atoms or groups, leading to a more stable configuration.

The Le Bel–Van 't Hoff rule, also known as the Le Bel-Van 't Hoff rule of stereochemistry, relates to the spatial arrangement of molecules and their optical activity. Specifically, it provides insight into the relationship between the number of stereocenters in a molecule and the number of possible stereoisomers.

The ligand cone angle is a concept used in coordination chemistry to describe the spatial orientation of ligands around a central metal ion in a coordination complex. It refers to the geometric representation of how ligands are arranged and the degree to which they can approach and interact with the central metal atom.

Molecular configuration refers to the three-dimensional arrangement of atoms within a molecule, particularly how these atoms are bonded together and oriented in space. This includes aspects such as: 1. **Bond Lengths**: The distances between the nuclei of bonded atoms. 2. **Bond Angles**: The angles formed between adjacent bonds at a particular atom. 3. **Dihedral Angles**: The angles between two plane sections formed by four atoms in a molecule.

The Natta projection is a stereochemical representation used to depict the three-dimensional arrangement of atoms in a polymer's repeating unit, particularly in the context of polymer chemistry where stereochemistry plays a significant role. Specifically, it is often associated with the structure of isotactic polypropylene, which is a type of polypropylene where all the methyl groups (–CH3) are arranged on the same side of the polymer chain.

A Newman projection is a way of visualizing the three-dimensional (3D) structure of organic molecules, particularly alkanes, in a two-dimensional (2D) format. It allows chemists to analyze the spatial arrangement of atoms and bonds around a specific bond between two carbon atoms. In a Newman projection, one looks straight down the axis of a particular bond (usually a carbon-carbon bond).

Noyori asymmetric hydrogenation is a chemical reaction developed by Japanese chemist Ryoji Noyori, which allows for the selective hydrogenation of prochiral ketones and other similar compounds to produce enantiomerically enriched alcohols. This reaction is particularly significant in the field of asymmetric synthesis, where the goal is to produce one specific enantiomer of a chiral product over the other.

Optical rotatory dispersion (ORD) is a phenomenon in which the optical rotation of a chiral substance varies with the wavelength of light. When plane-polarized light passes through a chiral medium, the plane of polarization is rotated by an amount that depends on the wavelength of the light. This effect is a consequence of the interaction between the light and the chiral molecules in the substance.

P-Chiral phosphines are a class of chiral ligands that are characterized by the presence of a phosphorus atom that is stereogenic (chiral). This means that the phosphorus center can exist in two non-superimposable mirror image forms, leading to different spatial arrangements of substituents attached to the phosphorus atom. In the context of coordination chemistry and catalysis, P-chiral phosphines are particularly valuable because they can impart stereochemical information to reactions, thereby enabling asymmetric synthesis.

Planar chirality refers to a type of spatial arrangement in certain molecules where the chirality arises from the planar structure of the molecule rather than from a chiral center (usually a carbon atom bonded to four different groups). In planar chirality, the different arrangements around a plane can lead to non-superimposable mirror images, typically as a result of the spatial arrangement of groups around a rigid planar structure, such as a cyclic compound or a flat molecular scaffold.

Protein primary structure refers to the unique sequence of amino acids that make up a protein. This sequence is determined by the genetic code and is crucial because it ultimately dictates how the protein will fold and function. Amino acids are linked together by peptide bonds to form a polypeptide chain, and the order of these amino acids is specified by the mRNA sequence during translation.

Protein quaternary structure refers to the highest level of structural organization in proteins, where two or more polypeptide chains, known as subunits, come together to form a larger, functional protein complex. Each subunit in a quaternary structure can consist of one or more polypeptide chains, and these subunits can be identical (homomeric) or different (heteromeric).

Pseudorotation is a term used in chemistry and molecular physics to describe a specific type of conformational change in certain cyclic compounds, particularly in the context of five-membered rings or certain larger rings. It involves the movement of atoms within the molecule that allows the structure to rotate around a particular axis, leading to a change in the arrangement of atoms or groups attached to the ring without breaking any bonds.

Pyramidal inversion is a phenomenon that occurs in certain molecules where the configuration of a chiral center can interconvert between two different arrangements. Specifically, this term is often used in the context of molecules that adopt a pyramidal geometry at a nitrogen or phosphorus atom. In a pyramidal structure, the central atom is bonded to three other atoms or groups in a manner that gives it a trigonal pyramidal shape, resembling a pyramid.

Racemic acid, also known as racemic tartaric acid, is a form of tartaric acid that consists of equal amounts of its two enantiomers: D-tartaric acid and L-tartaric acid. Tartaric acid is a naturally occurring organic acid that is commonly found in grapes and used in various food and beverage applications, particularly in winemaking.

The Skorokhod integral is a concept from the theory of stochastic calculus, specifically in the context of stochastic processes and integration with respect to semimartingales. It is named after the Russian mathematician R.S. Skorokhod, who made significant contributions to stochastic analysis.

The stochastic logarithm is a mathematical concept that arises in the field of stochastic calculus, specifically in the study of stochastic processes. It is used to analyze the logarithmic transformation of stochastic processes, especially when these processes are modeled as continuous-time martingales or processes with some form of randomness, such as Brownian motion. In a more formal sense, the stochastic logarithm refers to the logarithmic transformation applied to stochastic processes, particularly in the context of Itô's calculus.

The stereoelectronic effect refers to the influence of molecular geometry on electronic interactions and reactivity, particularly in the context of chemical bonding and reaction mechanisms. It describes how the spatial arrangement of atoms and the orientation of orbitals can affect the electronic properties of a molecule and, consequently, its reactivity. In essence, the stereoelectronic effect highlights the relationship between the arrangement of bonds in three-dimensional space and the electron distribution in molecular orbitals.