Laser flash photolysis study of the effects of substituents, solvents, and quenchers on the triplet state of benzaldehydes. H/D exchange following quenching by D/sub 2/O

Journal Article · Thu Oct 23 04:00:00 EDT 1986 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100280a098· OSTI ID:7169836

Goerner, H; Kuhn, H J

The deactivation pathways of the lowest triplet state of benzaldehyde (BA), a series of substituted derivatives (OCH/sub 3/, CH/sub 3/, F, Cl, Br, CHO, and CN), and some related aromatic aldehydes were examined at room temperature by laser flash photolysis in several solvents including water. The triplet state (lambda/sub max/ = 325 nm for BA in acetonitrile) was identified by energy-transfer measurements. The rate constant for self-quenching is below the diffusion-controlled limit (BA: < 1 x 10/sup 8/ M/sup -1/s/sup -1/). Triplet quenching by (heavy) water was observed for the benzaldehydes whose lowest triplet has n,..pi../sup */ character. On increasing the (H/sub 2/O/(CH/sub 3/CN) ratio the triplet life time (BA: 1.5 ..mu..s in acetonitrile, 60 ns in water) passes through a minimum. The apparent quenching constant (k/sub obsd/(H/sub 2/O)), which remains unchanged only between about 1 and 20% water content (BA: 3.0 x 10/sup 6/ M/sup -1/ s/sup -1/), shows an increasing trend for benzaldehydes with electron-withdrawing substituents and a decreasing trend with electron-donating substituents. Triplet quenching of benzaldehydes by D/sub 2/O leads to H/D exchange at the formyl group. A new pathway for the photodeuteriation is considered which bypasses the classical benzolyl-..cap alpha..-hydroxybenzyl radical pair.

• Research Organization: Max-Plank-Institut fuer Strahlenchemie, Muelheim a.d. Ruhr, West Germany
• OSTI ID: 7169836
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 90:22; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400202 -- Isotope Effects
Isotope Exchange
&amp; Isotope Separation
400500* -- Photochemistry
ALDEHYDES
BENZALDEHYDE
CHEMICAL REACTIONS
DATA
DE-EXCITATION
DECOMPOSITION
DEUTERIUM
ELEMENTS
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCIMER LASERS
EXPERIMENTAL DATA
GAS LASERS
HEAVY WATER
HYDROGEN
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
INFORMATION
ISOTOPES
ISOTOPIC EXCHANGE
LASERS
LIGHT NUCLEI
MEDIUM TEMPERATURE
MOLECULAR STRUCTURE
NONMETALS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
P STATES
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RADIATIONLESS DECAY
SOLVENT PROPERTIES
STABLE ISOTOPES
WATER