STERIC HINDRANCE Meaning and
Definition
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Steric hindrance refers to the phenomenon in organic chemistry where the spatial arrangement of atoms or groups of atoms within a molecule causes a decrease in the reactivity or accessibility of a specific site on the molecule. It is the result of repulsive forces or interactions between atoms or groups of atoms that are in close proximity to each other, preventing certain chemical reactions from occurring or reducing their efficiency.
In a molecule, steric hindrance occurs when bulky or large substituents are located near the reactive site, such as an active center or a reaction site. These bulky substituents create physical obstacles, inhibiting the approach of other molecules or reagents to the reactive site and thus impeding the reaction. The repulsive forces between the substituents can also strain chemical bonds in the molecule, making them more difficult to break.
Steric hindrance plays a crucial role in determining the selectivity and rate of many organic reactions. It can affect both intermolecular reactions between different molecules and intramolecular reactions within the same molecule. Steric hindrance is often encountered in organic synthesis when attempting to produce a specific compound through a particular reaction, as the steric constraints may hinder the desired transformation.
Understanding steric hindrance is essential for designing and predicting the outcomes of chemical reactions. Through the careful consideration and manipulation of substituents and reactive sites, chemists can strategically minimize or exploit the effects of steric hindrance to achieve desired molecular structures and reactions.
Etymology of STERIC HINDRANCE
The word "steric hindrance" is derived from the combination of two terms: "steric" and "hindrance".
1. Steric: The term "steric" originated from the Greek word "stereos", meaning "solid" or "three-dimensional". In chemistry, the term refers to the spatial arrangement or three-dimensional structure of molecules. It is often used to describe the repulsive interactions between non-bonded atoms or groups within a molecule, which can affect the molecule's shape and reactivity.
2. Hindrance: The term "hindrance" refers to an obstacle, obstruction, or impediment that prevents or slows down progress or movement. In chemistry, "hindrance" describes the effect of steric interactions on a chemical reaction.
