Skip to ContentGo to accessibility pageKeyboard shortcuts menu
OpenStax Logo
Organic Chemistry

7.1 Industrial Preparation and Use of Alkenes

Organic Chemistry7.1 Industrial Preparation and Use of Alkenes

7.1 • Industrial Preparation and Use of Alkenes

Ethylene and propylene, the simplest alkenes, are the two most important organic chemicals produced industrially. Approximately 220 million tons of ethylene and 138 million tons of propylene are produced worldwide each year for use in the synthesis of polyethylene, polypropylene, ethylene glycol, acetic acid, acetaldehyde, and a host of other substances (Figure 7.2).

Ethylene derivatives include ethanol, ethylene glycol, ethylene dichloride, acetaldehyde, acetic acid, ethylene oxide, vinyl acetate, polyethylene, and vinyl chloride. Propylene derivatives include isopropyl alcohol, propylene oxide, polypropylene, and cumene.
Figure 7.2 Compounds derived industrially from ethylene and propylene.

Ethylene, propylene, and butene are synthesized from (C2–C8) alkanes by a process called steam cracking at temperatures up to 900 °C.

An alkane consisting of 2 to 8 carbons undergoes steam cracking at 850-900 degrees Celsius to form hydrogen, ethene, propene, and butene.

The cracking process is complex, although it undoubtedly involves radical reactions. The high-temperature reaction conditions cause spontaneous breaking of C−C and C−H bonds, with the resultant formation of smaller fragments. We might imagine, for instance, that a molecule of butane splits into two ethyl radicals, each of which then loses a hydrogen atom to generate two molecules of ethylene.

Butane at 900 degrees Celsius forms two ethyl radicals, which convert to two ethene molecules and hydrogen.

Steam cracking is an example of a reaction whose energetics are dominated by entropy (ΔS°) rather than by enthalpy (ΔH°) in the free-energy equation ΔG° = ΔH° − TΔS° discussed in Section 6.7. Although the bond dissociation energy D for a carbon–carbon single bond is relatively high (about 370 kJ/mol) and cracking is endothermic, the large positive entropy change resulting from the fragmentation of one large molecule into several smaller pieces, together with the high temperature, makes the TΔS° term larger than the ΔH° term, thereby favoring the cracking reaction.

Order a print copy

As an Amazon Associate we earn from qualifying purchases.


This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's permission.

Want to cite, share, or modify this book? This book uses the Creative Commons Attribution-NonCommercial-ShareAlike License and you must attribute OpenStax.

Attribution information
  • If you are redistributing all or part of this book in a print format, then you must include on every physical page the following attribution:
    Access for free at
  • If you are redistributing all or part of this book in a digital format, then you must include on every digital page view the following attribution:
    Access for free at
Citation information

© Jan 9, 2024 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike License . The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.