ORG-15

Enantiomeric excess

ee = |R − S| / (R + S) × 100. Optical purity snapshot.

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StereochemistryEnantiomeric excess

Governing equation

ee=100\,|R-S|/(R+S)

where

R: R amount (—)
S: S amount (—)
ee: Enantiomeric excess (%)

Lecture brief

Historical brief

Hammett (1937) and Taft linear free-energy, E-factor green metrics, Woodward–Fieser UV and Claisen equilibria are how organic chemistry became predictive. The lab is substituent, waste and tautomer. This sheet (ORG-15 — Enantiomeric excess) is the form associated with Enantiomeric excess. Working symbols: $R$ , $S$ $\rightarrow$ $ee$ . For a linear polarimeter, ee ≈ observed [α] / [α] of the pure enantiomer.

Purpose

Purpose: compute

ee

from

R

S

in Organic chemistry via

ee=100\,|R-S|/(R+S)

ee = |R − S| / (R + S) × 100. Optical purity snapshot. Use it when a real organic chemistry question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

R = 0.800\,\mathrm{—}

S = 0.200\,\mathrm{—}

, the governing relation

ee=100\,|R-S|/(R+S)

yields

ee = 60.00\,\mathrm{%}

. Mole (or mass) fractions of the two enantiomers. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

R amount R0.8 —S amount S0.2 —

Outputs

Enantiomeric excess ee60.00 %

Reading speed

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Narration of this film

Mole (or mass) fractions of the two enantiomers.

For a linear polarimeter, ee ≈ observed [α] / [α] of the pure enantiomer.

Reading speed

Watch on YouTube