Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Photolysis matrices

Nitrogen extrusion has been used to make fragile molecules 2-thiirene (99) has been obtained by matrix photolysis of 1,2,3-thiadiazole (98), and azirines from 4//-triazoles (100 — 101). [Pg.528]

Thermolysis of thiadiazolines (22) in solution or under FVP conditions yields the corresponding thiiranes exclusively, whereas matrix photolysis in an organic glass or in solid argon allows the detection of thiocarbonyl ylides... [Pg.372]

There are also not very many data on the photolysis of 1,2,4-triazines. Many 1,2,4-triazines are not only stable to irradiation but they increase the photolytic stability of other systems. Meier tried to prepare trimethylazete (356) by matrix photolysis of trimethyl-1,2,4-triazine (355) but observed only the formation of 2-butyne, acetonitrile and nitrogen (80LA798). Photolysis of tris(heptafluoroisopropyl)-l,2,4-triazine (329) afforded tris(heptafluoroisopropyl)-l,3,5-triazine (357), nitrogen, perfluorobutyronitrile and bis(heptafluoroisopropyl)acetylene. The last three products are the same as in the pyrolysis of (329) <80JCS(P1)2254). [Pg.421]

The structure of benzyne, the parent member of the aryne group of intermediates, has been the focus of many experimental and theoretical studies. For instance, its IR spectrum has been recorded by low temperature solid matrix photolysis of precursors like benzocyclobutanedione (4) and diazalactone (S).6-9 Force field calculations based on these observations indicate an extended triple bond in benzyne (6a).10 Semiempirical and ab initio calculations also predict the arynic bond to be longer than a normal triple... [Pg.483]

Disilene and its isomer silylsilylene were neither available by standard vacuum flash pyrolysis of precursors 59-63, nor by the more elaborate method of pulsed flash pyrolysis of 60-63, a pulsed discharge in mixtures of argon and mono- and disilane74 or by the matrix photolysis of educts 59-66 using various light sources (Hg lamps, excimer laser)69,70,72, the microwave discharge in disilane 66 or the cocondensation of silicon atoms with SiFLt. [Pg.1156]

Examples of matrix-isolated silacarboxylic esters are scarce. Only the argon matrix photolysis of dimethoxysilylene (100) (cf Section VIII.E.2) results in the formation of infrared bands and a UV maximum (kmax = 232 nm) which are consistent with structure 101 (equation 26)107 108. [Pg.1162]

Also in 1992, Michl, Nefedov and coworkers20a,b reported that vacuum pyrolysis (800 °C, ] 0 1 - ] 0 4 Torr) of 5-silaspiro[4.4]nona-2,7-diene (12) resulted in the formation of silole (2), that was isolated in an Ar matrix, and characterized by its IR and UV-visible spectra. Matrix photolysis and vacuum pyrolysis of l,l-diazido-l-silacyclopent-3-ene (13) also produced the parent silole. After warming the pyrolysate to RT, the [2 + 4] dimer 10 of silole 2 was identified by GC-MS. [Pg.1967]

The S,N cleavage can also be accomplished by matrix photolysis of several heterocycles which undergo extrusion of N2 and CO to afford heterocumulenes334 (equation 64), characterized by UV and IR spectra (see Section II). [Pg.1422]

Argon matrix photolysis of tetrazolo[l,5-a]quinazoline/2-azidoquinazoline (96) gave a nitrene (97) which was observable by ESR, UV, and IR spectroscopy.81 The reactions of this nitrene were characterized and included fragmentation to radical species (98), rearrangement to cycloheptatetraene (99), and ring opening to a new nitrene (100). [Pg.168]

Cyclooctyne (14) is the smallest isolable unsubstituted cycloalkyne. In order to obtain spectroscopic evidence for the occurrence of smaller cycloalkynes, such as cycloheptyne (IS)12), 3,3,6,6-tetramethylcyclohexyne (17)12), cyclopentyne (18) 13> and acenaphthyne (19)13) matrix photolysis of the corresponding cyclopropenones was used. For example, in the photolysis of (21) in an argon matrix at 20 K a band at 2108 cm-1 of medium intensity was observed in the IR spectrum which was assigned to the C=C stretching vibration in (17)12). [Pg.193]

Photochemical behavior of monosilanes has been investigated by mercury-sensitized photolysis (15-19), flash photolysis (20, 21), vacuum ultraviolet photolysis (22-27), and matrix photolysis (28-30). The first examples of the photolysis of permethylated polysilanes were published in 1970 (14). All of the cyclic and acyclic permethylpolysilanes with the exception of hexamethyldisilane readily undergo photolysis on irradiation with ultraviolet light to give shorter chain compounds with the concurrent generation of the divalent silicon intermediate, dimethylsilylene (8). [Pg.52]

The matrix photolysis of 2,5-diiodothiophene, a possible precursor of 2,5-didehydrothiophene has been investigated <2006JOC9602>. [Pg.834]

Now it is possible to consider the mechanism of the molecular elimination process (eq. 23) in light of a new isomeric intermediate, hydroxymethylene (hCoH). In the low-temperature matrix photolysis of formaldehyde at 15 K, three sets of photochemical products were found (1) methanol and CO in solid formaldehyde (2) glycoaldehyde in a dilute Ar matrix and (3) hydroxyketene in a CO matrix (227). These observations were... [Pg.33]

Ikegami and Watanabe dia vered that l-benzyl-4-carbomethoxypyridinyl was unstable to light. In a matrix, photolysis of the radical led to methyl isonicotinate and benzyl radical (Eq. 21). [Pg.149]


See other pages where Photolysis matrices is mentioned: [Pg.43]    [Pg.127]    [Pg.270]    [Pg.131]    [Pg.131]    [Pg.131]    [Pg.138]    [Pg.140]    [Pg.243]    [Pg.844]    [Pg.43]    [Pg.127]    [Pg.43]    [Pg.127]    [Pg.389]    [Pg.87]    [Pg.88]    [Pg.199]    [Pg.288]    [Pg.270]    [Pg.196]    [Pg.3773]    [Pg.3774]    [Pg.3775]    [Pg.783]    [Pg.786]   
See also in sourсe #XX -- [ Pg.5 ]




SEARCH



Azides, matrix photolysis

Diazirine, matrix photolysis

Diazomethane matrix photolysis

Matrix photolysis, Wolff rearrangement

Thiazol-2-carboxylic acid matrix-isolated, photolysis

© 2024 chempedia.info