Principle of minimum structural change

Principle of minimum structural change
According to this oversimplified principle, chemical species do not isomerize in the course of a transformation, e.g. substitution, or the change of a functional group of a chemical species into a different functional group is not expected to involve the making or breaking of more than the minimum number of bonds required to effect that transformation. For example, any new substituents are expected to enter the precise positions previously occupied by displaced groups.[1]

Molecular rearrangements[2]  violates the so-called 'principle of minimum structural change'.

References: 

  1. IUPAC Goldbook, doi:10.1351/goldbook.M03997
  2. The term is traditionally applied to any reaction that involves a change of connectivity (sometimes including hydrogen)

Abegg's rule

Abegg's rule
Abegg's rule states the sum of the absolute values of the maximum positive and negative valence of an atom is often equal to eight.
  •  Abegg’s rule is sometimes referred to as "Abegg’s law of valence and countervalence".
  • for a given chemical element (as sulfur) Abegg’s rule states that the sum of the absolute value of its negative valence (such as −2 for sulfur in H2S) and its positive valence of maximum value (as +6 for sulfur in H2SO4) is often equal to 8.
  • The rule used a historic meaning of valence which resembles the modern concept of oxidation state in which an atom is an electron donor or receiver.

Abegg, Richard Wilhelm Heinrich

  • January 9, 1869 – April 3, 1910
  • Danish chemist, major work on chemical valence
  • Trained as organic chemist (student of August Wilhelm von Hofmann at the University of Berlin); but practiced  physical chemistry with Friedrich Wilhelm Ostwald in Leipzig, Germany

Read More

  1. Abegg, R. (1904). "Die Valenz und das periodische System. Versuch einer Theorie der Molekularverbindungen (The valency and the periodical system - Attempt on a theory of molecular compound)". Zeitschrift für anorganische Chemie 39 (1): 330–380. doi:10.1002/zaac.19040390125.
  2. Lewis, Gilbert N. (1916-04-01). "THE ATOM AND THE MOLECULE". Journal of the American Chemical Society 38 (4): 762–785. doi:10.1021/ja02261a002.
  3. Pauling, Linus (1960-06). The Nature of the Chemical Bond and the Structure of Molecules and Crystals; An Introduction to Modern Structural Chemistry. (3 ed.). Cornell University Press. ISBN 0-8014-0333-2. 
  4. http://en.wikipedia.org/wiki/Abegg%27s_rule
  5. http://www.springerreference.com/docs/html/chapterdbid/206127.html
  6. http://en.wikipedia.org/wiki/Richard_Abegg

Sir Chandrasekhara Venkata Raman, FRS

Indian Scientist

Sir Chandrasekhara Venkata Raman, FRS
Sir Chandrasekhara Venkata Raman, FRS
Sir Chandrasekhara Venkata Raman, FRS (7 November 1888 – 21 November 1970) was an Indian physicist whose work was influential in the growth of science. He was the recipient of the Nobel Prize for Physics in 1930 for the discovery that when light traverses a transparent material, some of the deflected light changes in wavelength. This phenomenon is now called Raman scattering and is the result of the Raman effect.


The Raman papers archive curated by Raman Research Institute, Bangalore, India. C.V. Raman and his work

Read more at ACS
the-raman-effect-commemorative-booklet
Raman Effect as the Chemist’s Tool

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