Classical conformational analysis of strained organic molecules. I. [l,m,n]Propellanes with l,m,n equal to 2, 3, and 4

✍ Scribed by Helena Dodziuk

• Book ID: 102879433
• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: English
• Weight: 508 KB
• Volume: 5
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.540050610

✦ Synopsis

Classical conformational analysis was applied to the study of the variation of heats of formation (HOF) and geometrical parameters of small-ring propellanes. As expected, the calculated HOF is the smallest for [4,4,4]propellane I and the largest for [2,2,2]propellane X. In spite of the different trends exhibited by the strain energy components, the calculated HOF values may be reproduced within a simple additivity scheme. The calculated bridgehead-bridgehead bond length is the longest for [2,2,2]propellane (1.655 A), lowers with increasing molecular size, and is equal to 1.558 A for [4,4,4]propellane. In agreement with experimental findings the latter value is significantly larger than the standard value of 1.54 A typical for unstrained hydrocarbons. Other calculated geometrical parameters as well as HOF values cannot be compared with experimental and/or theoretical results since there is a lack of reliable experimental data. Surprisingly, [2,2,2]propellane was found to be more flexible than the less strained bicyclo[2,2,2]octane.