Kinetic and mechanistic studies involving the nitroso group

Nitrosation is a major area of work in physical organic chemistry, which is of interest as an academic study in its own right but is also of wider interest owing to the carcinogenicity of some N-nitroso compounds. The present work has boon concerned with some of the reactions involving the nitroso group at nitrogen, oxygen and sulphur sites,, The approach has been to determine rate constants for the reactions involved and to use these to establish mechanism and relative reactivities. The work covers four areas; (i) Denitrosation of N-nitrosoamines in solvents other than water It has been found that some solvents do enhance the rate of denitrosation relative to that in water. (ii) Diazotisation of aromatic amines. This reaction proceeds via the formation of an N=nitroso intermediate. The relative reactivities of a number of nitrosating species in this reaction have been established. (iii) Nitrosation of thiols. Few kinetic studies have been made of S-nitrosation (compared to N-nitrosation), here the rates of reaction of some tbiocarboxylie acids toward nitrosating species have been determined and comparisons with other substrates drawn. (iv) Nitrosation of alcohols. The kinetics of nitrosation of alcohols has already been studied in some detail and here the aim has been to use this reaction to throw some light on the nature of the intermediate in aqueous nitrosation

Towards integrative neuromonitoring of the surgical newborn: A systematic review

BACKGROUND: The altered neurodevelopment of children operated on during the neonatal period might be due to peri-operative changes in the homeostasis of brain perfusion. Monitoring of vital signs is a standard of care, but it does not usually include monitoring of the br

The noise-lovers: cultures of speech and sound in second-century Rome

This chapter provides an examination of an ideal of the ‘deliberate speaker’, who aims to reflect time, thought, and study in his speech. In the Roman Empire, words became a vital tool for creating and defending in-groups, and orators and authors in both Latin and Greek alleged, by contrast, that their enemies produced babbling noise rather than articulate speech. In this chapter, the ideal of the deliberate speaker is explored through the works of two very different contemporaries: the African-born Roman orator Fronto and the Syrian Christian apologist Tatian. Despite moving in very different circles, Fronto and Tatian both express their identity and authority through an expertise in words, in strikingly similar ways. The chapter ends with a call for scholars of the Roman Empire to create categories of analysis that move across different cultural and linguistic groups. If we do not, we risk merely replicating the parochialism and insularity of our sources.Accepted manuscrip

Sodium salts of bis(1-dodecenylsuccinamic acids): A simple route to anionic gemini surfactants

New anionic gemini surfactants with low CMC values (ca. 10-4 mol dm-3) can be synthesized by a simple synthetic route using readily available reagents. The synthesis involves the reaction of a diamine with 2-dodecen-1-ylsuccinic anhydride to form a bis(1-dodecenylsuccinamic acid), which is neutralized to form the sodium salt. The product consists of a mixture of regioisomers, but the CMC values are consistent between samples

Lyotropic and interfacial behaviour of an anionic gemini surfactant

The sodium salt of N,N′-hexane-bis (1-dodecen-1-ylsuccinamic acid) is an anionic dimeric (gemini) surfactant. A flooding penetration scan of this surfactant in water demonstrates a sequence of lyotropic phases at room temperature (20 °C). Preparation of surfactant–water mixtures has resulted in a phase diagram which shows that the same sequence of phases exists up to 100 °C. These phases are tentatively assigned to the sequence: micellar to normal hexagonal (H1) to cubic (V1) to lamellar (Lα). The interfacial tension at the n-heptane/water interface has been determined in the presence of this surfactant. The surfactant head group area at the interface is large (2.8±0.3 nm2 at 298 K) and the interfacial tension above the critical micelle concentration is low (7 mN m−1), but considerably higher than the ultra-low values that have been reported for cationic dimeric surfactants at various hydrocarbon–water interfaces

Smectic phases observed in 1,1,2,2,-tetrahydroperfluoroalkyl-4-nitrobenzoates

On studying the thermal behaviour of a series of 1,1,2,2-tetrahydro-perfluoroalkyl 4-nitrobenzoates it was found that the decyl and dodecyl compounds showed smectic mesophases. This illustrates that a polar substituent in the 3-position of the aromatic ring for 1,1,2,2-tetrahydroperfluoroalkylbenzoates is not a requirement for thermotropic behaviour

Synthesis and evaluation of novel side chain liquid crystal polymers with a single aromatic unit

Polyacrylates with a 3-nitro-4-(1,1,2,2- tetrahydroperfluroalkyl) benzoate unit as a side chain substituent have been synthesised. These materials form rare examples of side chain thermotropic polymers containing a single aromatic unit. These polymers form smectic phases only.The phase behaviour has been investigated by optical microscopy and d.s.c

Thermotropic perfluoroalkyl azobenzoates. Studies of low molar mass compounds and side chain polymer derivatives

A series of 4′-[(carbonyloxy-1,1,2,2 Tetrahydrofluorodecyl)]-4 -(ω-bromo-alkenyloxy) azobenzenes, 4′-[(carbonyloxy-1,1,2,2-Tetrahydrofluorodecyl)]-4-(alk-1-enyloxy) azobenzenes have been synthesized. Also, a polyacrylate has been formed by phase transfer catalyzed reaction between one of the ω-bromo-alkenyloxy compounds and sodium polyacrylate as well as two polysiloxanes formed by hydrosilylation of the alkenyloxy compounds and a polyhydrosilane. All of the low molar mass compounds show the S A phase on heating and an increase in perfluoroalkyl chain length results in an increase in clearing temperature whilst an increase in the hydrocarbon chain length shows a decrease in clearing temperature. Upon grafting these low molar mass units to a polymer backbone, the resulting materials also show smectic mesophases despite having quite low clearing entropies (ΔS/R to approximately 0.2-0.6). The precursor polymers are of low molar mass (Mw 1200-1800 g mol -1) and this may be the reason why the polymers do not show glass transition temperatures

Synthesis of poly vinyl ethers with pendant non-linear optical azo dyes

Two vinyl ether polymers with pendant 4′-amino-4-nitroazobenzene dyes were synthesized with different lengths of spacer from the main chain. The synthesis involved polymerization of 2-chloroethylvinyl ether with HI/I 2 to give a polymer of M n 13200 and M w/M n 1.23. The azo-dye molecules were attached to this polymer backbone by a Williamson ether synthesis route using a propyl or hexyl alcohol derivative of the azo dye. High loading of the dyes (> 75%) was achieved as measured by visible spectrophotometry, elemental analysis and 1H-NMR. The polymers exhibit high solubility in a range of solvents and thermal stability up to 200° in air. Liquid crystal (nematic) behaviour is observed for these polymers on cooling from the isotropic melt phase