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

$E_s \in \left[-3, 0.5\right]$

where

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

The figure, part by part

Each numbered marker wears the color of its card. Hover a card to light the marker. Tap a marker to jump to that card. The slider walks a red point along the curve; Animate drawing traces it like a pen.

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①

Governing law — red

\log(k/k_0)=\delta E_s

$E_s \in \left[-3, 0.5\right]$

$E_s = -3$ $k = 0.001$

Along the curve

②

Domain of the variable — blue

E_s_{\min} = -3,\quad E_s_{\max} = 0.5

$E_s \in \left[-3, 0.5\right]$

$E_s = -3$ $E_s = -3$

Along the curve

③

Response curve — green

\log(k/k_0)=\delta E_s

$E_s \in \left[-3, 0.5\right]$

$E_s = -3$ $k = 0.001$

Along the curve

④

Rate of change — amber

\frac{\mathrm{d}k}{\mathrm{d}E_s}

$E_s \in \left[-3, 0.5\right]$

$E_s = -2.978$ $k^{\prime} = 0.002$

Along the curve

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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