Related Experiment Video
Updated: Jun 13, 2026
08:56
Synthesis of a Borylated Ibuprofen Derivative Through Suzuki Cross-Coupling and Alkene Boracarboxylation Reactions
Published on: November 30, 2022
Borane-lewis base complexes as homolytic hydrogen atom donors.
Johnny Hioe1, Amir Karton, Jan M L Martin
1Department Chemie und Biochemie, LMU München, Butenandtstrasse 5-13, 81377 München, Germany.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|May 8, 2010
Summary
Radical stabilization energies were calculated for boryl radicals. Borane complexes with heterocycles show high stabilization, indicating spin delocalization is key to radical stability.
Area of Science:
- Computational chemistry
- Quantum chemistry
- Radical stabilization
Background:
- Boryl radicals are key intermediates in various chemical reactions.
- Understanding their stabilization is crucial for controlling reaction pathways.
- Lewis base complexation is a known method for radical stabilization.
Purpose of the Study:
- To calculate radical stabilization energies (RSE) for boryl radicals complexed with Lewis bases.
- To investigate the relationship between RSE and Lewis acid-Lewis base interactions.
- To elucidate the mechanisms of radical stabilization in these complexes.
Main Methods:
- Utilized the G3(MP2)-RAD level of theory for RSE calculations.
- Referenced calculations to the B-H bond dissociation energy (BDE) of BH(3) at the W4.3 level.
- Analyzed charge- and spin-density distributions.
Main Results:
- High RSE values were observed for borane complexes of five- and six-membered heterocyclic Lewis bases.
- These high RSE values correlate with strong Lewis acid-Lewis base complex formation.
- Spin delocalization within the boryl radical complexes was identified as a major stabilization mechanism.
Conclusions:
- Borane complexes with heterocyclic Lewis bases exhibit significant radical stabilization.
- The strength of Lewis acid-Lewis base interactions directly influences radical stabilization.
- Spin delocalization plays a critical role in stabilizing boryl radicals.
More Related Videos
Related Concept Videos
03:08Hydroboration-Oxidation of Alkenes
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
02:33Lewis Acids and Bases
In 1923, G. N. Lewis proposed a generalized definition of acid-base behavior in which acids and bases are identified by their ability to accept or to donate a pair of electrons and form a coordinate covalent bond.
A coordinate covalent bond (or dative bond) occurs when one of the atoms in the bond provides both bonding electrons. For example, a coordinate covalent bond occurs when a water molecule combines with a hydrogen ion to form a hydronium ion. A coordinate covalent bond also results when...
A coordinate covalent bond (or dative bond) occurs when one of the atoms in the bond provides both bonding electrons. For example, a coordinate covalent bond occurs when a water molecule combines with a hydrogen ion to form a hydronium ion. A coordinate covalent bond also results when...
02:16Lewis Acids and Bases
This lesson delves into Lewis acids and bases in the context of the octet rule for electron-deficient compounds. Here, the concept is discussed, emphasizing the group 13 elements like boron or aluminium. Since group 13 elements possess three valence electrons, they form trivalent compounds with a sextet of electrons and a vacant orbital for the central atom. Consequently, these electron-deficient compounds accept electrons from other species to complete their octet in a chemical reaction. They...
02:36Regioselectivity and Stereochemistry of Hydroboration
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
02:55Exceptions to the Octet Rule
Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:
00:54Radical Formation: Homolysis
A bond is formed between two atoms by sharing two electrons. When this bond is broken by supplying sufficient energy, either two electrons can be taken up by one atom forming ions by the cleavage called heterolysis, or the two electrons are shared by two atoms, with one each creating radicals by the cleavage called homolysis.