In nucleophilic aromatic photosubstitution, just as in aromatic substitution in the ground state, substituents can have directing and activating effects. Four rules, which describe orientation of nucleophilic substitution in the excited state, can now be formulated. They are: (a) meta-activation by the nitro group (b) ortho/para-activation by the methoxy group (and probably also by other electr...

The adjective "aromatic" is used by organic chemists in a rather different way than it is normally applied. It has its origin in the observation that certain natural substances, such as cinnamon bark, wintergreen leaves, vanilla beans and anise seeds, contained fragrant compounds having common but unexpected properties. Cinnamon bark, for example, yielded a pleasant smelling compound, formula C...

Many aromatic compounds and their monomers are existing in nature. Besides they are introduced into the environment by human activity. The conversion of these aromatic compounds is mainly an aerobic process because of the involvement of molecular oxygen in ring fission and as an electron acceptor. Recent literatures indicated that ring fission of monomers and obligomers mainly occurs in anaerob...

Aromatic compounds comprise a wide variety of natural and synthetic compounds that can serve as substrates for bacterial growth. So far, four types of aromatic metabolism are known. (1) The aerobic aromatic metabolism is characterized by the extensive use of molecular oxygen as cosubstrate for oxygenases that introduce hydroxyl groups and cleave the aromatic ring. (2) In the presence of oxygen,...

Mechanisms of bone invasion by squamous carcinomas of the head and neck have, been investigated using fresh tumours and established tumour cell lines in an in vitro bone resorption assay with 45Ca-labelled mouse calvaria. Fresh tumours regularly resorb bone in vitro. Activity is consistently reduced by indomethacin. The tumours release E2 prostaglandins (PGE2) in amounts sufficient to account f...

Rice (Oryza sativa L.) is enjoyed by many people as a staple food because of its flavour and texture. Some cultivars, like scented rice, are preferred over others due to their distinctive aroma and flavour. The volatile profile of rice has been explored by other investigators, some of whom have also determined a corresponding aroma using GC/olfactometry. However, little research has been done t...