Acetaldehyde: right to roam

shutterstock176140355300tb

Source: © Shutterstock

A surprising new insight into photolysis

Australian and US chemists have re-shaped our understanding of an important photochemical reaction that defies classical transition state theory and proceeds via multiple barrierless ‘roaming’ pathways.

Traditional teaching has it that chemical reactions proceed from reactants to products via a transition state, and must overcome an energy barrier associated with bond breakage in the reactant species. In recent years, a new class of reaction pathway known as roaming has emerged. Roaming reactions do not follow such a clearly defined pathway, and can be thought of as ‘barrierless’. Developing products do not have sufficient translational energy to fully separate, causing the insipient hydrogen atom to ‘roam’ around the formyl radical (CHO) until an abstraction reaction results in the formation of carbon monoxide and hydrogen gas.

Scott Kable, at the University of New South Wales, Australia, and international collaborators, probed the rotational and translational distributions of acetaldehyde photolysis products methane and carbon monoxide to settle the matter. 

This article provides a link to coverage by Chemistry World

Thanks for using Education in Chemistry. You can view one Education in Chemistry article per month as a visitor. 

A photograph of a teacher standing in a white lab coat, speaking with a class of children in a laboratory, is superimposed on a colourful background. Text reads "Teach Chemistry means support for classroom and staff room".

Register for Teach Chemistry for free, unlimited access

Registration is open to all teachers and technicians at secondary schools, colleges and teacher training institutions in the UK and Ireland.

Get all this, plus much more:

  • unlimited access to resources, core practical videos and Education in Chemistry articles
  • teacher well-being toolkit, personal development resources and online assessments
  • applications for funding to support your lessons

Already a Teach Chemistry member? Sign in now.

Not eligible for Teach Chemistry? Sign up for a personal account instead, or you can also access all our resources with Royal Society of Chemistry membership.