https://web.iitd.ac.in/~arunku/files/CEL311_Y13/Adsorption%20Theory%20to%20practice_Dabrowski.pdf

Adsorption — from theory to practice

Life on earth is based on compounds that have carbon frames and backbones. Today, chemists have added to the world of biomolecules and biopolymers approximately 107 different synthetic molecules and polymers, the structures of which also depend on the formation of strong, stable carbon–carbon bonds. Although the stability of carbon–carbon bonds has been recognized for more than a century, the two natural modifications graphite and diamond were, until recently, the only allotropic forms of carbon on earth that were available in macroscopic quantities and were structurally well characterized. With the synthesis of macroscopic quantities of buckminsterfullerene (C60) and the higher fullerenes (C70, C76, C78, etc.) and the exploration of the fascinating properties of these all-carbon spheres, this situation has completely changed. In the coming decades, the design, preparation, and study of novel molecular and polymeric allotropic forms of carbon will be a central topic in chemistry. Research in this area will dramatically advance the fundamental knowledge on carbon-based matter and, as already illustrated by the ongoing work on C60, generate unprecedented technological perspectives. This review surveys synthetic organic-chemical approaches toward the preparation and study of all-carbon molecules and polymers that differ from the familiar networks of graphite and diamond as well as from the fullerenes. We will also discuss the ongoing research on fullerenes with a particular focus on the synthetic approaches to these all-carbon spheres and their transition metal complexes.

Synthetic approaches toward molecular and polymeric carbon allotropes

Synthesis and Applications

This Minireview highlights recent advances in the field of aryne and cyclohexyne chemistry that have allowed the extraordinary reactivity of these entities to be harnessed during the course of natural product syntheses. The syntheses presented rely on the use of these reactive species in chemoselective transformations and follow unprecedented synthetic strategies that are inspiring for the practitioners of synthetic organic chemistry.

Arynes and cyclohexyne in natural product synthesis.

The 351 nm photoelectron spectra of the negative ions of o-, m-, and p-benzyne (1,2-, 1,3-, and 1,4-dehydrobenzene, respectively) and their perdeuterated isotopomers have been obtained. The o-benzyne ions were generated by the reaction of benzene and benzene-d6 with O-, while the m- and p-benzyne ions were prepared by the gas-phase reaction between the corresponding 3- and 4-(trimethylsilyl)phenyl anions and molecular fluorine, F2. The photoelectron spectra of the benzyne anions each contain two features, corresponding to formation of the singlet and triplet states of the biradicals. The electron affinities of o- and p-benzyne are found to be 0.564 ± 0.007 and 1.265 ± 0.008 eV, respectively, while the electron affinities of deuterated o- and p-benzyne are found to be 8 and 5 meV lower, respectively. The electron affinity of m-benzyne could not be determined from the photoelectron spectrum because the origin peak could not be assigned unequivocally. For o- and p-benzyne, the singlet−triplet energy splittin...

Ultraviolet Photoelectron Spectroscopy of the o-, m-, and p- Benzyne Negative Ions. Electron Affinities and Singlet−Triplet Splittings for o -, m -, and p -Benzyne

Benzyne, cyclohexyne, and 3-azacyclohexyne have been obtained by flash vacuum pyrolysis of phthalic anhydride, 4-cyclopentylidene-3-methylisoxazol-5(4H)-one (34), and 3-methyl-4-(2-pyrrolidinylidene)isoxazol-5(4H)-one (37), respectively, isolated at 77 K and observed by IR spectroscopy. Trapping and fragmentation reactions are described, and the implications for the mechanism of benzyne formation from phthalic anhydride via cyclopentadienylideneketene (9) are discussed.

Benzyne, cyclohexyne, and 3-azacyclohexyne and the problem of cycloalkyne versus cycloalkylideneketene genesis

Acyl‐ and Thioacylketenes: Synthesis of 3‐Benzoly‐4‐phenylthiet‐2‐one

Benzothiet-2-one (5) is obtained as a neat solid, stable below -20 °C (-45 °C in solution), by flash vacuum pyrolysis of benzothiophene-2,3-dione (9). Naphtho[2,3-b]thiet-2-one (21) and naphtho[2,l-b]thiet-l-one (42) are obtained as stable crystalline solids in near-quantitative yields from the corresponding napthothiophenediones 20 and 41. Naphtho[2,3-b]oxet-2-one (31) and naphtho[2,3-b]azetin-2-one (36) were generated and observed by IR spectroscopy to be stable below -40 °C and 0 °C, respectively. The thietones, oxetones, and azetinones undergo rapid ring-opening reactions with methanol to give the corresponding carboxylic acid esters. They undergo thermal CO elimination with concomitant Wolff-type ring contraction to thioketenes (17, 25, 45), ketenes (30), and nitriles (37), respectively. The di-, oligo-, and polymerization of the thietones has been elucidated. Naphtho[2,l-b]thiet-l-one (42) reacts with 1-thiocarbonyl-lH-indene (45) to give cycloaddition product 46. Naphthothietones 21 and 42 react with dicyclohexylcarbodiimide to furnish 2-imino-l,3-thiazin-4-one derivatives 47 and 49.

Gerhard Gross

Papers

Benzyne, cyclohexyne, and 3-azacyclohexyne and the problem of cycloalkyne versus cycloalkylideneketene genesis

Acyl‐ and Thioacylketenes: Synthesis of 3‐Benzoly‐4‐phenylthiet‐2‐one

Benzothiet-2-ones: Synthesis, Reactions, and Comparison with Benzoxet-2-ones and Benzazetin-2-ones

Regioselective Synthesis and Antiviral Activity of Purine Nucleoside Analogues with Acyclic Substituents at N7

1,2‐Cyclohexadiene