The photochemical nucleophile+lefin combination, aromatic substitution (photo-NOCAS) reaction of methanol, 2,6-dimethyl-l,6-heptadiene, and 1,4-dicyanobenzene yields three distinct types of I: 1 : 1 adducts:an acyclic product, 4-(l-methoxymethyl-1,5-dimethyl-5-hexenyl)benzonitrile (8,5%); a cis-trarzs pair of cyclohexanes, 4-(3-methoxymethyl-1,3-dimethylcyclohexyl)benzonitrile (9 cis (12%) and 9 trans (1 1%)); and a cis-trans pair of cycloheptanes, 4-(4-methoxy-l,4-dimethylcycloheptyl)benzonitrile (10 cis ( 12%) and 1 0 trans (10%)). Variation in the concentration of the nucleophile, methanol, and codonor, biphenyl, affects the product ratio and it has been possible to establish the mechanisms for the formation of these products. The acyclic product is formed by a typical photo-NOCAS reaction, that is, addition (anti-Markovnikov) across one of the heptadiene double bonds. The cyclohexane products are formed following 1,6-erzdo cyclization of the intermediate P-alkoxy radical. And the cycloheptane products result from 1,7-e~zdo,e~zdo cyclization of the initially formed 2,6-dimethyl-l,6-heptadiene radical cation. Comparison of the relative rates of these cyclization processes can be made with those of the next smaller homolog, 2,5-dimethyl-1,5-hexadiene.Key tvords: photochemistry, photoinduced electron transfer, radical ions, radicals, cyclization.RCsumC : La rCaction de substitution aromatique par combinaison photochimique nuclCophile-olCfine (photo-NOCAS) du mCthanol avec le 2,6-dimethylhepta-l,6-dikne et le 1,4-dicyanobenzkne conduit B trois types distincts d'adduits 1 : 1 : 1 : un produit acyclique, le 4-(I-mCthoxymCthyl-I,5-dimkthylhex-5-6nyl)benzonitrile (8.5%); une paire de cyclohexanes cis-trans, les 4-(3-mCthoxymCthyl-1,3-dimCthylcyclohexyl)benzonitriles (9 cis (12%) and 9 trans (1 1%)) et une paire de cycloheptanes cis-tratzs les 4-(4-mCthoxy-l,4-dimCthylcyclohepty1)benzonitriles (10 cis (12%) and 1 0 trans (10%)). Des variations dans la concentration du nuclCophile, du mCthanol et du co-donneur, le biphCnyle, affectent les concentrations relatives des produits et il a CtC possible d'Ctablir les mCcanisme de formation de ces produits. Le produit acyclique se forme par une rkaction photo-NOCAS typique, & savoir une addition (anti-Markovnikov) sur les doubles liaisons de l'heptadikne. Les produits cyclohexaniques se forment par une cyclisation 1,6-endo du radical intermkdiaire P-alkoxy. Et les produits du cycloheptane rksultent d'une cyclisation 1,7-etzdo,endo du cation radical 2,6-dimkthylhepta-l,6-dikne qui se forme initialement. On peut faire une comparaison des vitesses relatives de ces divers processus de cyclisation avec celles observCes pour I'homologue infkrieur immCdiat, le 2,5-dimkthylhexa-l,5-dikne.

Chitosan has been investigated as an inexpensive, biologically derived adsorbent and/or primary coagulant for two reactive azo dyes in textile wastewater. At natural pH, complete elimination of colour was achieved from 0.1 g/L aqueous solutions of the textile dyes Procion Orange MX-2R and Procion Red MX-5B with a dose of 6 g of chitosan per litre of dye solution. However, when pH was lowered (to 4.8 and 5.5 respectively), a dose of only 1 g of chitosan per litre was necessary to eliminate colour and drastically reduce TOC (total organic carbon) and chemical oxygen demand for the same concentration of dyes. This allowed about an 80% reduction in sludge volume production. Addition of sodium phosphate dibasic and potassium sulfate improved the dye removal at higher pH. Colour removal decreased significantly with or without added salts as pH was adjusted above 7. Equilibrium adsorption experiments showed that both dye solutions follow the Freundlich isotherm, but not the Langmuir isotherm. Kinetics measurements show a better fit to the pseudosecond-order Lagergren model than to the first-order Lagergren model. Brunauer-Emmett-Teller, or BET, surface area analysis and scanning electron microscope micrographs were included for better understanding of the nature of the chitosan surface with and without adsorbed dye. Chitosan appears to be a natural, clean and excellent product for the adsorption of Procion Orange MX-2R and Procion Red MX-5B in mildly acidic conditions.

A batch monopolar reactor was developed for total phosphorus (TP) recovery using electrochemical struvite precipitation. This study involves the optimization of factors using response surface methodology to maximize the TP recovery. The optimal parameters for this study were found to be a pH of 8.40, a retention time of 35 min, a current density of 300 A/m2, and an interelectrode distance of 0.5 cm, resulting in 97.3% of TP recovery and energy consumption of 2.35 kWh/m3. A kinetic study for TP removal revealed that at optimum operating conditions, TP removal follows second‐order kinetics (removal rate constant(K) = 0.0117 mg/(m2·min)). The system performance was compared to the performance of an iron electrocoagulation system. The composition of the precipitate obtained during the optimal runs were analyzed using X‐ray diffraction and EDS analysis. X‐ray diffraction analysis of the magnesium precipitate revealed the presence of struvite as the only crystalline compound. Practitioner Points Electrochemical struvite precipitation has the potential to recover total phosphorus from anaerobic bioreactor effluent. Optimum conditions for phosphorus recovery was found at a pH of 8.4, retention time of 35 min, current density of 300 A/m2, and interelectrode distance of 0.5 cm. The quadratic model predicted complete (100 %) TP recovery under optimized conditions, whereas 97.3 % recovery was observed under experimental conditions. TP removal under optimum conditions followed second‐order rate equation (removal rate constant(K) = 0.0117 mg/(m2·min)). XRD analysis of the precipitate revealed struvite as the only crystalline compound.

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When an acetonitrile solution (no added methanol) of 1.4-dicyanobenzene (I), biphenyl (5), and (R)-(+)-a-terpineol (22) was irradiated under these conditions, the products were the cyclized 1: 1 (22: 1) photo-NOCAS adducts: (1R,2S,5R)-2-(4-cyanophenyl)-2,6,6-trimethyl-7-oxabicyclo[3.2.l]octane (27,2l%) and (lS,4R,6R)-6-(4-cyanophenyl)-l,3,3-trimethyl-2-oxabicyclo[2.2.2]octane (28,2%). Structural assignments were based primarily upon detailed analysis of 'H and I3c nmr spectra and, for four of the products (24,26,27, and 28), structures were firmly established by X-ray crystallography. The mechanism for the formation of these products is discussed, with emphasis on the intramolecular reactions of the intermediate alkene radical cations. Molecular mechanics (MM3) calculations gave information regarding the structure and energy of the conformers of 21 and 22 that was useful for predictinglexplaining the observed reactivity on thebasis of approach vector analysis; the transition state for cyclization incorporates the nucleophile and the alkene radical cation carbon atoms at the vertices of an obtuse triangle orthogonal to the plane of the T-system. This is also Part 38 of the series Radical ions in photochemistry; see refs. 1 and 2 for preceding parts of these series.