Enantiomer Excess

Enantiomer excess (ee) is a quantitative measure of the imbalance between two enantiomers in a chiral mixture, indicating how far its composition departs from a racemic mixture. It is calculated from their relative amounts as ee = |R − S|/(R + S) × 100%, so a racemate has 0% ee and a single enantiomer has 100% ee. Chemists determine ee using methods such as chiral chromatography, NMR with chiral reagents, or polarimetry, depending on the system. In chemistry, ee helps evaluate asymmetric synthesis and separation methods, assess product purity, and interpret stereochemical composition in pharmaceutical and biological research.

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JoVE Core - Organic Chemistry

Naming Enantiomers

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2023

The naming of enantiomers employs the Cahn–Ingold–Prelog rules that involve assigning priorities to different substituent groups at a chiral center. Each enantiomer, being a distinct molecule, is assigned a unique name by the Cahn–Ingold–Prelog (CIP) rules, also called the R–S system. The prefix R- or S- attached to the chiral centers in an enantiomer is dependent on the spatial arrangement of the four substituents on the chiral center. The R–S system essentially comprises three steps:...

Excess Reserves

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2025

Excess reserves, while often viewed as idle funds from a lending perspective, play a vital role in ensuring financial stability and managing risk—particularly during periods of economic uncertainty or regulatory change.Strategic Value Beyond LiquidityExcess reserves are not merely a liquidity buffer; they represent a deliberate strategic decision by banks. When economic conditions are stable, lending typically yields higher returns. However, during periods of financial volatility or increased...

Properties of Enantiomers and Optical Activity

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2023

It is essential to understand the difference between chiral and achiral interactions and the implications thereof in optical activity and their applications. Just as our feet, which are chiral, interact uniquely with chiral objects, such as a pair of shoes, but identically with achiral socks, enantiomers of a molecule exhibit different properties only when they interact with other chiral media. An example of a significant implication from this facet is the phenomenon known as optical activity,...

Racemic Mixtures and the Resolution of Enantiomers

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2025

A racemic mixture, or racemate, is an equimolar mixture of enantiomers of a molecule that can be separated using their unique interaction with chiral molecules or media. Racemic mixtures are denoted by the (±)- prefix. This ‘optical rotation descriptor’ applies to the whole solution of a racemic mixture rather than a specific stereoisomer. Enantiomers typically have the same physical and chemical properties. Hence, they are not easily separable. However, enantiomers can exhibit different...

Excess Pressure Inside a Drop and a Bubble

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2023

The shape of a small drop of liquid can be considered spherical, neglecting the effect of gravity. This drop can further be considered as two equal hemispherical drops put together due to surface tension. The forces acting on the spherical drop are due to the pressure of the liquid inside the drop, the pressure due to air outside the drop, and the force due to the surface tension acting on the two hemispherical drops. where γ corresponds to the surface tension. Recalling that the force per...

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