Modification of photochemical reactivity through the use of clathrates: the Norrish type I and type II reactions in Dianin's compound

1985 ◽  
Vol 63 (10) ◽  
pp. 2719-2725 ◽  
Author(s):  
P. C. Goswami ◽  
Paul de Mayo ◽  
N. Ramnath ◽  
G. Bernard ◽  
N. Omkaram ◽  
...  
Keyword(s):  
Inclusion Complexes ◽  
Hydrogen Abstraction ◽  
Photochemical Reactions ◽  
Type I ◽  
Type Ii ◽  
Guest Molecules ◽  
Photochemical Reactivity ◽  
Norrish Type ◽  
Restricted Environment ◽  
Dianin's Compound

Dianin's compound (4-p-hydroxyphenyl-2,2,4-trimethylchroman) serves as host in a series of well-defined clathrate inclusion complexes with eleven linear, as well as branched chain, phenyl alkyl ketone guest molecules, chosen for their ability to undergo the Norrish type I and type II photochemical reactions in solution. The photochemical reactivity of the guest ketones within the clathrate cavity was determined by irradiation of the inclusion complexes in the solid state. The results were compared to the photoreactivity of the ketones in polar as well as nonpolar liquid media. In general, the inclusion complex medium brings about an enhancement of type I over type II reactivity and causes an increase in type II fragmentation compared to type II cyclization. This change in reactivity is interpreted as resulting from the relatively restricted environment of the clathrate cavity coupled with the greater motion required for the type II process (γ-hydrogen abstraction) compared to the type I reaction (α-cleavage), as well as from the greater steric requirements for type II cyclization (cyclobutanol formation) as compared to type II cleavage (1,4-hydroxybiradical scission).

Photolysis of 4-Methyl 3-Hexanone and 2-Methoxy 3-Pentanone in Hydrocarbon Solution

1971 ◽  
Vol 49 (8) ◽  
pp. 1310-1314 ◽  
Author(s):  
L. P-Y. Lee ◽  
B. McAneney ◽  
J. E. Guillet
Keyword(s):  
Quantum Yield ◽  
Hydrogen Abstraction ◽  
Type I ◽  
Type Ii ◽  
Cage Effect ◽  
Predominant Type ◽  
Norrish Type ◽  
Hydrocarbon Solution ◽  
Membered Transition State ◽  
Made In

Studies of the photolysis of 4-methyl 3-hexanone and the iso-electronic 2-methoxy 3-pentanone have been made in hydrocarbon solution using light of wavelength 313 nm. The latter compound gives only Norrish type II products with a quantum yield of 0.19 ±.01. The former gives a predominance of type I products with a total quantum yield of 0.23 ±.01 and the quantum yield for type II is reduced to 0.10 ±.01. The predominant type I reaction appears to involve α-scission to give an ethyl and a 2-methyl butyryl radical, which suggests a "cage effect". It is suggested that the reason for the suppression of the type I reaction in 2-methoxy 3-pentanone is the greater ease of γ-hydrogen abstraction due to the presence of the oxygen atom in a six-membered transition state.

Modification of photochemical reactivity by zeolites: Norrish type I and type II reactions of benzoin derivatives

1988 ◽  
Vol 110 (14) ◽  
pp. 4848-4849 ◽  
Author(s):  
D. R. Corbin ◽  
D. F. Eaton ◽  
V. Ramamurthy
Keyword(s):  
Type I ◽  
Type Ii ◽  
Photochemical Reactivity ◽  
Norrish Type

Modification of photochemical reactivity by zeolites. Norrish type I and type II reactions of ketones as photochemical probes of the interior of zeolites

1990 ◽  
Vol 55 (18) ◽  
pp. 5269-5278 ◽  
Author(s):  
V. Ramamurthy ◽  
D. R. Corbin ◽  
D. F. Eaton
Keyword(s):  
Type I ◽  
Type Ii ◽  
Photochemical Reactivity ◽  
Norrish Type

ChemInform Abstract: Modification of Photochemical Reactivity by Zeolites: Norrish Type I and Type II Reactions of Benzoin Derivatives.

ChemInform ◽  
1988 ◽  
Vol 19 (45) ◽  
Author(s):  
D. R. CORBIN ◽  
D. F. EATON ◽  
V. RAMAMURTHY
Keyword(s):  
Type I ◽  
Type Ii ◽  
Photochemical Reactivity ◽  
Norrish Type

scholarly journals Non-adiabatic dynamic of atmospheric unimolecular photochemical reactions of 4,4-difluoro-crotonaldehyde using TD-DFT and TSH approaches

2021 ◽  
Author(s):  
Pedro J Castro Pelaez ◽  
Satoshi Maeda ◽  
Keiji Morokuma
Keyword(s):  
Degrees Of Freedom ◽  
Hydrogen Abstraction ◽  
Electronic States ◽  
Photochemical Reactions ◽  
Type I ◽  
Excitation Energies ◽  
Geometrical Structures ◽  
Photochemical Processes ◽  
Norrish Type ◽  
Global Reaction

Photochemical reactions of small molecules occur upon irradiation by ultraviolet or visible light, and they are a very important and controversial chemical process in the Earth’s atmosphere because they impact our quality of life and health. Small-unsaturated carbonyl compounds play an important role in the chemistry of the polluted troposphere. The fluorinated aldehydes are very reactive under the sunlight driving to species that trigger more atmospheric reactions. This paper is focused on a theoretical study of the photochemistry of difluoro-crotonaldehyde using static and dynamic calculations by combination of Global Reaction Route mapping (GRRM) and Trajectory Surface Hopping (TSH) approach. The static analysis of the electronic and geometrical structures at the critical points allowed to rationalize the possible pathways that interconnect the stationary and crossing points in order to get a map of the unimolecular photochemical reactions which take place. The time evolution of the electronic states and the degrees of freedom enabled the identification of the requirements to follow the most probable deactivation pathways. This article reports the unimolecular deactivation pathways after the electronic excitation of the trans and cis isomers. In both cases, the excitation energies were calculated and compared with the analogous in the crotonaldehyde in order to elucidate the effect of fluorine atoms on the electronic structure and stabilities. After the initial excitations to the ππ* excited states, the main deactivation channels follow non-adiabatic pathways via S/S conical intersections. Ultrafast processes leading to the early activation of the S govern the decay of the difluoro-crotonaldehyde. Depending on the nature of the S state before the crossing with the S, the system can follow several reaction pathways. The main photochemical processes observed were the cis-trans isomerization, the Norrish type I reaction (α-cleavage), Norrish type II reaction (γ-hydrogen abstraction) and fluorine photodissociation. The time scale, the molecular deformations and the electronic states implied for the different photochemical processes, as well as how these compete with the photophysical deactivation are discussed.

The photochemical reactivity of some benzoylthiophenes. IV. The effect of an adjacent methyl group on the excited state reactivity of 3-benzoylthiophene

1978 ◽  
Vol 56 (15) ◽  
pp. 1970-1984 ◽  
Author(s):  
D. R. Arnold ◽  
C. P. Hadjiantoniou
Keyword(s):  
Hydrogen Abstraction ◽  
Thiophene Ring ◽  
Emission Spectra ◽  
Photochemical Reactions ◽  
Triplet States ◽  
Photochemical Reactivity ◽  
Methyl Group ◽  
State Diagrams ◽  
Phosphorescence Emission ◽  
Intramolecular Hydrogen

The electronic absorption and phosphorescence emission spectra and the photochemical reactivity of several methyl-3-benzoylthiophenes (2- and 4-methyl-3-benzoylthiophene (1, 2), 2,5-dimethyl-3-benzoylthiophene (3), and 3-(2-methylbenzoyl)thiophene (4)) have been studied. Partial state diagrams have been constructed. The lowest energy absorption in hexane solution in every case is the carbonyl n → π* transition. The two lowest triplet states of these ketones are close in energy and, in fact, the nature of the emitting triplet (n,π* or π,π*) depends upon the position of methyl substitution and upon the solvent. The photochemical reactions studied include intramolecular hydrogen abstraction (revealed by deuterium exchange in the adjacent methyl group upon irradiation in perdeuteriomethanol solution), photocycloaddition of dimethyl acetylenedicarboxylate to the thiophene ring, and photocycloaddition of isobutylene to the carbonyl group. Generalizations, potentially useful for predicting photochemical reactivity of these and other aromatic ketones are summarized.

Norrish Type II Photochemical Reactions

2007 ◽  
pp. 1
Author(s):  
S. V. Ley ◽  
L.-G. Milroy ◽  
R. M. Myers
Keyword(s):  
Photochemical Reactions ◽  
Type Ii ◽  
Norrish Type

Molecular photochemistry. XLVIII. Type I and type II photochemical reactions of some five- and six-membered cycloalkanones

1971 ◽  
Vol 93 (26) ◽  
pp. 7213-7221 ◽  
Author(s):  
J. C. Dalton ◽  
K. Dawes ◽  
N. J. Turro ◽  
D. S. Weiss ◽  
J. A. Barltrop ◽  
...  
Keyword(s):  
Photochemical Reactions ◽  
Type I ◽  
Type Ii
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