The research work reported in the thesis comprises two parts. In the first part the reaction of ortho-phthaldehyde with urea, thiourea and their N-alkyl/aryl derivatives is conducted in acidic and basic media. The resulting chromogens and non-chromogens compounds are separated by physical, chemical and various kinds of chromatographic techniques and structure are elucidated by all means of spectroscopy and a single X-ray crystallography. After identification of compounds, the methods for the determination of urea present in biological samples are worked out; this will help in modification of existing clinical techniques used for exact diagnosis of various diseases. Biological properties of the compounds (isoindolines, benzodiazepines and isobenzofuran) obtained from the above said reactions are evaluated. In the second part of the thesis functionalised diarylcarbenes are synthesized which are excellent reactive intermediates suitable for the direct surface modification of organic polymers which are in fact used to introduce urea and thiourea functions onto polystyrene at loading levels of up to 2.3 x 1013 molecules/cm2. Surface modification is confirmed by different spectral and non-spectral techniques (ATR-IR, XPS & elemental analysis). The moidifed polymers are capable of reversible binding and release of peroxide at loading levels of up to 0.6 mmol/g, and polymers display biocidal activity against a spectrum of Gram-positive and Gram-negative bacteria.