ORG-18

Aromatic bromination snapshot

r = k [ArH][Br2]. Electrophilic aromatic substitution rate.

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KineticsElectrophilic aromatic

Governing equation

r=k[\mathrm{ArH}][\mathrm{Br}_2]

where

k: Rate constant (L/(mol·s))
[ArH]: Arene (mol/L)
[Br_2]: Bromine (mol/L)
r: Rate (mol/(L·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-18 — Aromatic bromination snapshot) is the form associated with Electrophilic aromatic. Working symbols: $k$ , $[ArH]$ , $[Br_2]$ $\rightarrow$ $r$ . The Wheland intermediate is the RDS for many ArH. Activating groups raise k.

Purpose

Purpose: compute

r

from

k

[ArH]

[Br_2]

in Organic chemistry via

r=k[\mathrm{ArH}][\mathrm{Br}_2]

r = k [ArH][Br2]. Electrophilic aromatic substitution 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

k = 0.400\,\mathrm{L/(mol·s)}

[ArH] = 0.200\,\mathrm{mol/L}

[Br_2] = 0.050\,\mathrm{mol/L}

, the governing relation

r=k[\mathrm{ArH}][\mathrm{Br}_2]

yields

r = 0.00400\,\mathrm{mol/(L·s)}

. Second-order snapshot, no catalyst term. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Rate constant k0.4 L/(mol·s)Arene [ArH]0.2 mol/LBromine [Br_2]0.05 mol/L

Outputs

Rate r0.00400 mol/(L·s)

Reading speed

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Narration of this film

Second-order snapshot, no catalyst term.

The Wheland intermediate is the RDS for many ArH. Activating groups raise k.

Reading speed

Watch on YouTube