Chemistry of bis(2-ethynyl-3-thienyl)arene and related systems. Part 6: preparation of 1,4-bis(2-ethynyl-3-thienyl)benzene derivatives containing fluorine atoms at the 2,3- or 2,5-positions of the benzene ring

2009 ◽  
Vol 30 (3-4) ◽  
pp. 351-359 ◽  
Author(s):  
Kozo Toyota ◽  
Yasutomo Tsuji ◽  
Noboru Morita
Keyword(s):  
Benzene Ring ◽  
Benzene Derivatives

scholarly journals Ring Contraction Reactions of a Non-Benzenoid Aromatic Cation and a Neutral Homoaromatic System into Benzene Derivatives

2021 ◽  
Author(s):  
Demelza Lyons ◽  
An Huy Dinh ◽  
Nhan Nu Hong Ton ◽  
Reece Crocker ◽  
Binh Khanh Mai ◽  
...  
Keyword(s):  
Organic Chemistry ◽  
Benzene Ring ◽  
Benzene Derivatives ◽  
Ring Contraction ◽  
Chemistry Research ◽  
Synthetic Utility ◽  
Aromatic Ions ◽  
Benzyl Halides ◽  
Tropylium Salts ◽  
Ring Contraction Reaction

Aromaticity is one of the most intriguing concepts in organic chemistry. Simple and extended benzenoid aromatic systems have been very well established in undergraduate textbooks, and there are also mentions of non-benzenoid aromatic structures such as cyclopropenium, cyclopentadienide and cycloheptatrienylium (tropylium) ions. However, the structural relationship and the comparison of stabilization energy of such aromatic ions to benzene ring have been rarely studied and remained an underexplored area of advanced organic chemistry research. To contribute some insights into this topic, we focused on the chemical transformation, namely a ring contraction reaction, of the tropylium ion to benzene ring in this work. With an approach combining computational studies with experimental reactions, we also aim to turn this transformation into a synthetically useful tool. Indeed, this work led to the development of a new synthetic protocol, which involved an oxidative ring-contraction of tropylium ion, to formally introduce the phenyl ring onto a range of organic structures. Furthermore, the homoaromatic cycloheptatrienyl precursors of tropylium salts used in these reactions can also be rearranged to valuable benzhydryl or benzyl halides, enriching the synthetic utility of this ring-contraction protocol.

The Responses of Onion and Lily Mitosis to Coumarin and Parasorbic Acid

1947 ◽  
Vol 23 (3-4) ◽  
pp. 292-297
Author(s):  
IVOR CORNMAN
Keyword(s):  
Aqueous Solution ◽  
Benzene Ring ◽  
Lactone Ring ◽  
Saturated Solution ◽  
Saturated Aqueous Solution ◽  
Benzene Derivatives ◽  
Binucleate Cells

1. In Allium and Lilium roots, saturated aqueous solution of coumarin produced a disruption of the metaphase typical of many benzene derivatives, viz. suppression of the spindle, splitting and shortening of the chromosomes, with retarded division of the centromere. The resultant polyploid nuclei and binucleate cells resumed division when the roots were returned to water. 2. Saturated solution of parasorbic acid slowed Allium mitosis, but caused no abnormalities. 3. Both coumarin and parasorbic acid eventually prevented the inception of mitosis, and this suppression of prophases persisted for several hours after removal of the agent. 4. The results are in agreement with prior evidence that in some configurations the benzene ring disrupts mitosis whereas the lactone ring inhibits growth.

Carbon-13 Substituent-Induced Chemical Shifts: Monosubstituted Benzene Derivatives

1992 ◽  
Vol 57 (3) ◽  
pp. 497-507 ◽  
Author(s):  
Otto Exner ◽  
Miloš Buděšínský
Keyword(s):  
Benzene Ring ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
The Other ◽  
Correlation Equations ◽  
Benzene Derivatives ◽  
Complex Mechanism ◽  
Monosubstituted Benzene ◽  
Resonance Effects ◽  
Other Hand

Carbon-13 NMR spectra of twelve monosubstituted benzene derivatives were measured in deuterochloroform. Together with the literature data a set of 35 systematically chosen substituents was obtained on which some thirty correlation equations were tested. As anticipated only substituent chemical shifts (SCS) in the position 4 are controlled by inductive and resonance effects, and can be correlated by dual substituent parameters (DSP). For the other positions DSP were not successful and more sophisticated equations are not much telling. On the other hand, the direct relations between two series of SCS are usually more precise and simple to understand. It is concluded that SCS in benzene ring need not be controlled by too complex mechanism but simply by different factors than by inductive and resonance effects.

Photochemistry of halogenated benzene derivatives. Part VI. Photoreactions of tetra-and pentachlorophenols in water–acetonitrile mixtures

1985 ◽  
Vol 63 (2) ◽  
pp. 469-475 ◽  
Author(s):  
Ghulam Ghaus Choudhry ◽  
Frans W. M. van der Wielen ◽  
G. R. Barrie Webster ◽  
Otto Hutzinger
Keyword(s):  
Benzene Ring ◽  
Reductive Dechlorination ◽  
Benzene Derivatives ◽  
Aqueous Acetonitrile ◽  
Acetonitrile Solutions

Laboratory photochemical studies of aqueous acetonitrile solutions of some polychlorinated phenols (PCPs) such as 2,3,4,5-tetrachlorophenol (2,3,4,5-Cl4-Pn) (1), 2,3,4,6-Cl4-Pn (2), 2,3,5,6-Cl4-Pn (3), and pentachlorophenol (Cl5-Pn) (4) at λ > 285 nm have been carried out for 6 and 24 h exposure times. All the investigated PCPs underwent reductive dechlorination. This process was dependent not only upon the position of OH group but also upon the relative positions of the Cl substituents on the benzene ring. The Cl4-Pn 2 (and 3) and Cl5-Pn (4) also yielded photoproducts of molecular formulae C8H4Cl3NO (M+• = 235) and C8H3Cl4NO (M+• = 269), respectively. Furthermore, phenol 3 is unique amongst the investigated PCPs; in addition to the above mentioned photoproducts, it yielded hexa-, hepta-, and octachlorodihydroxybiphenyl(s) as well as heptachlorohydroxydiphenyl ether.

scholarly journals Molecular structure as determined by a new electron diffraction method II—The halogen-carbon bond distance in some simple benzene derivatives

1934 ◽  
Vol 146 (858) ◽  
pp. 690-700 ◽  
Keyword(s):  
Molecular Structure ◽  
Electron Diffraction ◽  
Benzene Ring ◽  
Phase 1 ◽  
Bond Distance ◽  
Diffraction Method ◽  
Vapour Phase ◽  
Constant Independent ◽  
Benzene Derivatives ◽  
Carbon Bond

The object of this investigation was to get replies to the following questions concerning the structure of certain simple benzene derivatives in the vapour phase:— (1) Is the benzene ring a flat, regular hexagon? (2) What is the carbon-carbon distance in the benzene ring, and is this a constant independent of the number of substituents ?

scholarly journals The structure of the benzene ring in C 6 (CH 3 ) 6

1929 ◽  
Vol 123 (792) ◽  
pp. 494-515 ◽  
Keyword(s):  
Benzene Ring ◽  
Structure Determination ◽  
Unit Cell ◽  
The Other ◽  
Benzene Derivatives ◽  
Benzene Nucleus ◽  
Alternative Structures ◽  
Graphite Structure ◽  
Crystalline Benzene ◽  
The Difference

Since benzene itself is not crystalline at ordinary temperatures the study of the benzene nucleus or ring has had to be referred to certain of its derivatives. The most hopeful line of attack appeared to be in the direction of the fully substituted derivatives, such as C 6 Cl 6 , or else by way of compounds such as naphthalene and anthracene which contain more than one ring. The results so far obtained, however, have only shown that the ring is centro-symmetrical, a fact confirmed by the recent examination of crystalline benzene itself, that its approximate width (given by the difference in lengths of the naphthalene and anthracene molecules) is 2∙49 Å., and that there exist in the nucleus two periodicities of about 1∙28 and 2∙66 Å. If the ring be supposed to consist of six carbon atoms of diameter 1∙54 arranged as in the diamond pattern, then periodicities of 1∙26 and 2∙52 would exist, the width of the ring itself being 2∙52. If, on the other hand, the benzene nucleus is a plane ring of six carbon atoms of diameter 1∙42, such as occurs in the graphite structure, then the periodicities would be 1∙23 and 2∙46, the width of the ring being 2∙46 (fig. 1). The experimental observations ( loc. cit .) could not definitely decide between these alternative structures, and no other criterion was found which would distinguish with certainty between a puckered and a plane ring. One of the chief difficulties encountered in the study of these various benzene derivatives was that the unit cell invariably contained more than one molecule, a fact which necessarily complicated any structure determination by introducing the question of relative orientations.

Infrared spectra of phenylboronic acid (normal and deuterated) and diphenyl phenylboronate

1968 ◽  
Vol 46 (12) ◽  
pp. 2089-2095 ◽  
Author(s):  
J. A. Faniran ◽  
H. F. Shurvell
Keyword(s):  
Hydrogen Bonding ◽  
Benzene Ring ◽  
Infrared Spectra ◽  
Phenylboronic Acid ◽  
Intramolecular Hydrogen Bonding ◽  
Benzene Derivatives ◽  
Monosubstituted Benzene ◽  
Intramolecular Hydrogen

The infrared spectra of phenylboronic acid, normal and deuterated, and diphenyl phenylboronate have been recorded in the range 4000–300 cm−1 and assignments of the observed frequencies have been made. The spectrum of the acid in the OH stretching region shows evidence of intramolecular hydrogen bonding. The spectrum of diphenyl phenylboronate has been interpreted by analogy with monosubstituted benzene derivatives. The two different environments of the phenyl groups in this molecule give rise to splitting of two of the characteristic vibrations of the benzene ring near 760 and 680 cm−1.

The excited state antiaromatic benzene ring: a molecular Mr Hyde?

2015 ◽  
Vol 44 (18) ◽  
pp. 6472-6493 ◽  
Author(s):  
Raffaello Papadakis ◽  
Henrik Ottosson
Keyword(s):  
Excited State ◽  
Benzene Ring ◽  
Excited States ◽  
Benzene Derivatives

Baird's rule tells that benzene is an antiaromatic “Mr Hyde” in its lowest excited states, explaining many photoreactions of benzene derivatives.

Electron Microscopic and Isozyme Study of a Case of Ochronosis

1972 ◽  
Vol 30 ◽  
pp. 88-89
Author(s):  
Jay W. Cha ◽  
Perry J. Melnick
Keyword(s):  
Benzene Ring ◽  
Enzyme System ◽  
Homogentisic Acid ◽  
Degenerative Changes ◽  
Acid Oxidase ◽  
Electron Microscopic ◽  
Tyrosine Metabolism ◽  
Collagenous Tissues

Hereditary ochronosis in very few cases has been examined electron microscopically or histochemically. In this disease homogentisic acid, a normal intermediary of tyrosine metabolism, forms in excessive amounts. This is believed to be due to absence or defective activity of homogentisic acid oxidase, an enzyme system necessary to break the benzene ring and to further break it down to fumaric and acetoacetic acids. Ochronotic pigment, a polymerized form of homogentisic acid, deposits mainly in mesenchymal tissues. There has been a question whether the pigment originates from the collagenous tissues, or deposits passively, where in contrast to melanin it induces degenerative changes.

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