An Introduction to the Consequences of Spin and Bond Strength in the Chemistry of Diatomic Oxygen, Peroxides, and Related Species

Abstract

This review chapter discusses oxygen and peroxides in organic chemistry. Numerous types of oxygen species are described including ions, radicals, biradicals, and zwitterionic species; examples of such species are superoxide anion (O 2 ⋅− ), dioxygenyl cation (O 2 ⋅+ ), ozone (O 3 ), oxygen oligomers (O x ), and the lowest excited singlet state of oxygen ( 1 Δ). An analysis of acyclic peroxides and cyclic peroxides (e.g., 1,2‐dioxetanes,1,2,3‐trioxolanes, and 1,4‐endoperoxides) is provided. Isoelectronic heteroatom structures and other analogs are also provided to help guide thinking for the factors that underlie the stability of peroxide and other oxygen‐containing species.

On thein vivophotochemical rate parameters for PDT reactive oxygen species modeling

“…The electronic behavior of molecular oxygen results from the arrangement of two electrons in the outer π g shell (it has a total of 16 electrons since Z = 8 for each O atom) (Kasha, 1985; Greer et al , 2014). Molecular oxygen has an electron configuration in which orbitals are designated as even parity (g = gerade) or odd parity (u = ungerade):…”

“…The second singlet excited state ( 1 Σ g + ) is located 37 kcal/mol (1.6 eV, λ = 755 nm) above the ground state. Quenching of the excited photosensitizers of a high enough energy by the ground state molecular oxygen produces both forms of singlet oxygen (Greer et al , 2014). Because 1 Δ g oxygen lifetimes are in the microsecond range they can undergo bimolecular reactions; in contrast, the 1 Σ g + oxygen lifetime is short (in the pico- to nanosecond range) (Weldon et al , 1999) and thus chemically unreactive.…”

Using Singlet Oxygen to Synthesize Natural Products and Drugs

“…Historically, 1 O 2 showed diffusible properties with photosensitization as a convenient method for its production in the Foote–Wexler reaction 50 years ago. , Since that time, 1 O 2 has been established for its ability to oxidize organic and biological compounds − or to be used in synthesis.…”

Lipophilic Decyl Chain–Pterin Conjugates with Sensitizer Properties

“…Nucleoside analogues have been synthesized as pterin derivatives . In the presence of oxygen, aromatic pterins act as photosensitizers through both type I (generation of radicals via electron transfer or hydrogen abstraction) and type II (production of 1 O 2 ) mechanisms; , the former species (such as hydroxyl radicals) have very short diffusion distances, but the latter species 1 O 2 can diffuse one hundred or more nanometers in biological media. , Pterins are reported to photosensitize oxidation of biomolecules, such as nucleotides, DNA, amino acids, peptides, proteins, , and biomembranes . Relatedly, pterins have been found to induce the photokilling of cervical cancer (HeLa) cells upon UVA irradiation, and alter the integrity of the cell membranes, among other deleterious aspects .…”