ORG-11

Taft steric Es

log(k/k0) = δ Es. Steric attenuation of a rate.

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Physical organicTaft Es

Governing equation

\log(k/k_0)=\delta E_s

where

\delta: Steric sensitivity (—)
E_s: Taft Es (—)
k_0: Reference rate (1/s)
k: Rate (1/s)

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-11 — Taft steric Es) is the form associated with Taft Es. Working symbols: $\delta$ , $E_s$ , $k_0$ $\rightarrow$ $k$ . Es is negative for bulky groups (Me = 0, t-Bu ≈ −1.5). δ > 0 if the reaction is sterically hindered.

Purpose

Purpose: compute

k

from

\delta

E_s

k_0

in Organic chemistry via

\log(k/k_0)=\delta E_s

log(k/k0) = δ Es. Steric attenuation of a rate. 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

\delta = 1.000\,\mathrm{—}

E_s = -0.500\,\mathrm{—}

k_0 = 1.000\,\mathrm{1/s}

, the governing relation

\log(k/k_0)=\delta E_s

yields

k = 0.3162\,\mathrm{1/s}

. Aliphatic series, steric part only. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Steric sensitivity \delta1 —Taft Es E_s-0.5 —Reference rate k_01 1/s

Outputs

Rate k0.3162 1/s

Reading speed

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Narration of this film

Aliphatic series, steric part only.

Es is negative for bulky groups (Me = 0, t-Bu ≈ −1.5). δ > 0 if the reaction is sterically hindered.

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