Aromaticity and Antiaromaticity of Four-Membered P-Heterocycles

Abstract

The organophosphorus chemistry became the one of the most rapidly developing and very important subdiscipline in the organic and organometallic chemistry. This development is providing exciting chemical structures, efficient metal ligands and biologically important pharmacophores. In the present review we first collected and discussed the fourmembered antiaromatic organic and inorganic compounds, containing phosphorous atom in their ring, which were considered and prepared during the past half a century.

Energy Managements in the Chemical and Biochemical World, as It may be Understood from the Systems Chemistry Point of View

“…Interesting examples can be found in phosphorous organic compounds [7][8][9]19], one of them is exemplified in Figure 5. weak aromaticity may be due to the pyramidal geometry around the P atom since the lone electron pair cannot effectively participate in the delocalization.…”

“…Several studies revealed that contrary to the stability of phosphole (13) Figure 5). The instability of 17 was explained by the existing weak antiaromaticity [9,19]. …”

“…7; Figure 8-TOP] of the compound examined, comparing to reference compounds 19 and 20. The ∆H H2 (AM) value for dimethylacetamide (19) is used to define perfect amidic character (Eq. 8.; AM % = +100%), while azaadamantane-2-on (20) represents complete absence of amidic character (AM % = 0%) [10].…”

“…A systemic approach is required to answer these. Making use of the recently established methodology [15][16][17][18][19] , hydrogenation reactions were used to determine aromaticity, amidicity and olefinicity values. …”

“…These organic functional groups may easily be described by the concept of 'conjugativicity'; a term analogous to aromaticity, 15 amidicity, 16,17 carbonylicity 18 and olefinicity. 19 Accordingly, the structure of NAD + and related models I-III (106, 112, 114, 116) are composed of an aromatic (pyridine) and most of them an amidic part; each described using aromaticity and amidicity parameters, respectively. The structure of NADH and its related models I-III (107, 113, 115, 117) are composed of one amidic and two olefinic parts, described by one amidicity and two olefinicity parameters, respectively.…”