Sequence Rules (Cahn–Ingold–Prelog Rules) assign R or S configuration to chiral centers based on priority of substituent groups. These rules are used to assign priorities to groups around a chiral center when determining R/S configurations. Sequence Rules: Priority by atomic number: Higher atomic number = higher priority. I > Br > Cl > S > … Read more
D-L System of Nomenclature (Fischer Nomenclature) classifies chiral molecules based on the spatial arrangement of groups around the asymmetric carbon. What is it? The D-L system is a historical method used to designate the configuration of chiral molecules, particularly sugars and amino acids. It is based on the molecule’s similarity to glyceraldehyde, the simplest chiral … Read more
Presentation of Molecules refers to different ways of representing molecular structures, such as Fischer, Newman, Sawhorse, and wedge-dash projections. Presentation of Molecules Wedge-Dash (3D) Projection Purpose: Shows the actual 3D spatial orientation of atoms or groups. Features: Solid wedge (▲): Bond coming out of the plane (towards you) Dashed wedge (▿ or dashed line): Bond … Read more
Chiral and Achiral Molecules: Chiral molecules have a non-superimposable mirror image due to a chiral center, while achiral molecules are superimposable on their mirror image and lack chirality. Chiral Molecules Definition: A molecule is chiral if it: Has no element of symmetry Is not superimposable on its mirror image Can rotate plane-polarized light (optically active) … Read more
Elements of Symmetry are geometric features like planes, axes, or centers that describe balance and repetition in a molecule’s structure. An element of symmetry is a feature (like a plane, point, or axis) that describes how a molecule can be transformed into an indistinguishable configuration. A molecule is achiral if it has any element of … Read more
Diastereomerism is a type of stereoisomerism where molecules have the same molecular formula but are not mirror images of each other. Unlike enantiomers, diastereomers differ in physical and chemical properties such as melting point, solubility, and reactivity. This distinction makes diastereomerism important in drug design, as different diastereomers of the same compound may show varied … Read more
Definition of Meso Compounds: A meso compound is a special type of stereoisomer that contains multiple chiral centers but is nevertheless achiral as a whole. In other words, it has chiral centers, but due to an internal plane of symmetry (or another element of symmetry), the molecule is superimposable on its own mirror image. Identifying … Read more
Definition of the Enantiomers: Enantiomers are non-superimposable mirror images of each other. They have the same molecular formula and connectivity but differ in the spatial arrangement of groups around chiral centers. Key characteristics: Same physical properties (boiling point, melting point, solubility, etc.) Same chemical properties in achiral environments. Opposite optical rotation: One is dextrorotatory (+), … Read more
Optical Isomerism is a type of stereoisomerism where compounds differ in how they rotate plane-polarized light due to chiral centers. Definition of Optical Isomerism: Optical isomerism occurs when molecules can exist in two (or more) non-superimposable forms (stereoisomers) that differ in the way they interact with plane-polarized light. If a molecule can rotate the plane … Read more
Stereoisomerism is a form of isomerism in which molecules have: The same molecular formula The same sequence of bonded atoms (i.e., the same structural formula) But a different spatial arrangement of atoms or groups in 3D space So, unlike structural (constitutional) isomers, stereoisomers differ only in how atoms are oriented in space, not in how … Read more
