The Chemistry of Dimethyl Carbonate
Dimethyl carbonate (DMC) is a versatile compound that represents an attractive eco-friendly alternative to both methyl halides (or dimethyl sulfate) and phosgene for methylation and carbonylation processes, respectively. In fact, the reactivity of DMC is tunable: at T = 90 °C, methoxycarbonylations take place, whereas at higher reaction temperatures, methylation reactions are observed with a variety of nucleophiles. In the particular case of substrates susceptible to multiple alkylations (e.g., CH2-active compounds and primary amines), DMC allows unprecedented selectivity toward mono-C- and mono-N-methylation reactions. Nowadays produced by a clean process, DMC possesses properties of nontoxicity and biodegradability which makes it a true green reagent to use in syntheses that prevent pollution at the source. Moreover, DMC-mediated methylations are catalytic reactions that use safe solids (alkaline carbonates or zeolites), thereby avoiding the formation of undesirable inorganic salts as byproducts. The reactivity of other carbonates is reported as well: higher homologues of DMC (i.e., diethyl and dibenzyl carbonate), are excellent mono-C- and mono-N-alkylating agents, whereas asymmetrical methyl alkyl carbonates (ROCO2Me with R ≥ C3) undergo methylation processes with a chemoselectivity up to 99%.[1]
Dimethyl sulphoxide: A review of its applications in cell biology
Dimethyl sulphoxide is a water miscible solvent that has wide applications in cell biology. It acts as a cryoprotective agent in a variety of cells and tissues allowing prolonged storage at subzero temperatures. The action of dimethyl sulphoxide on the stability of the liquid matrix of cell membranes appears to be responsible for its effects and this appears also to be true for related effects on membrane permeability and fusion. Dimethyl sulphoxide is also known to act as an inducer of cellular differentiation and as a free radical scavenger and radioprotectant. A review of the underlying molecular basis of all these effects of dimethyl sulphoxide is presented.[2]
Dimethyl Sulfide Production in Marine Phytoplankton
Significant dimethyl sulfide (DMS) production is confined to a few classes of marine phytoplankton, mainly the Dinophyceae (dinoflagellates) and the Prymnesiophyceae (which includes the coccolitnophores). One hundred and twenty-three individual clones of phytoplankton representing twelve algal classes were examined in exponential growth for intra- and extracellular DMS (and its precursor DMSP). There is a strong correlation between the taxonomic position of the phytoplankton and the production of DMS. Although the Dinophyceae and Prymnesiophyceae predominate, other chromophyte algae (those possessing chlorophylls a and c) also contain and release significant amounts of DMS, including some members of the Chrysophyceae and the Bacillariophyceae (the diatoms). The chlorophytes (those algae possessing chlorophylls a and b) are much less significant producers of DMS with the exception of a few very small species. Other classes, including the cryptomonads and the cyanobacteria, are minor producers.[3]
Mortality Rate of Clarias gariepinus Fingerlings Exposed to 2, 3- dichlorovinyl dimethyl Phosphate
2, 3- dichlorovinyl dimethyl phosphate is an organophosphate insecticide used in the control of insects in both agricultural and household. This study investigated the mortality rate of Clarias gariepinus fingerlings exposed to 2, 3- dichlorovinyl dimethyl phosphate. Samples Clarias gariepinus were bought from a private fish farm in Yenagoa metropolis, Nigeria. The fishes were acclimatized in the laboratory for 3 days. A static renewal bioassay methodology was adopted. Results showed mortality rate of 32.85, 57.14 and 72.86% at 0.20, 0.60 and 1.00 ppm respectively (based on different concentration) and 32.67, 43.33, 56.67 and 73.33% respectively at intervals of 12, 24, 48 and 96 hours (based on time). There was significance difference (P<0.05) with respect to concentration, time and interaction of time/concentration. Results also showed increased mortality with increased concentration and exposure duration. The results showed that even at low concentration, 2, 3- dichlorovinyl dimethyl phosphate could still induce mortality in fingerlings of Clarias gariepinus. As such caution should be exercised in the use and disposal of empty cans of 2, 3- dichlorovinyl dimethyl phosphate close to aquatic-systems.[4]
Comparison of Chemical and Antimicrobial Studies of Egyptian Mandarin Leaves and Green Branches Volatile Oil
Aims: In the present study we compared the chemical composition and the antimicrobial activity of the essential oils isolated from green branches and leaves of mandarin.
Study Design: Extraction of essential oils from mandarin green branches and leaves by hydrodistillation
Place and Duration of Study: leaves and green branches were collected from Benha City, Qualyobia, Egypt in December 2012.
Methodology: The essential oils (EOs) isolated from mandarin (Citrus reticulata) were analyzed by GC and GC/MS. The antimicrobial activity was assessed using agar well diffusion method.
Results: Sixteen compounds were identified from the oil of branches which represented about 92% of the total detected constituents. The major components of the oil were dimethyl anthranilate (34.7%), γ-terpinene (33.6%) and limonene (11.2%). Alpha pinene and sabinene were present in considerable amounts (both at 2.8%). Other components were present in amounts less than 2%. From the heavier of layer mandarin leaves oil, thirteen compounds accounting for 95.4% of the oil were identified. Dimethyl anthranilate (65.3%) was the major component, followed by γ-terpinene (19.8%) and limonene (4.5%).
On the other hand, fourteen compounds (94.7%) were identified from the lighter layer of mandarin leaves oil including dimethyl anthranilate (60.6%), γ-terpinene (22.8%) and limonene (5.3%).
The antimicrobial activities of the oils were assessed. The antifungal activity was studied against Trichophyton mentagrophytes, Aspergillus fumigatus and Candida albicans. The antibacterial activities were measured against Staphylococcus aureus, Streptococcus pyogenes, Enterococcus faecalis as gram (+) bacteria; and Klebsiella pneumonia, Escherichia coli, Salmonella typhimurium as gram (-) bacteria.
Conclusion: The heavier layer of mandarin leaves oil was the most effective layer against all tested microorganisms, followed by the branches oil and finally the lighter layer of leaves oils.[5]
Reference
[1] Tundo, P. and Selva, M., 2002. The chemistry of dimethyl carbonate. Accounts of chemical research, 35(9), pp.706-716.
[2] Yu, Z.W. and Quinn, P.J., 1994. Dimethyl sulphoxide: a review of its applications in cell biology. Bioscience reports, 14(6), pp.259-281.
[3] Keller, M.D., Bellows, W.K. and Guillard, R.R., 1989. Dimethyl sulfide production in marine phytoplankton.
[4] Ojesanmi, A.S., Richard, G. and Izah, S.C., 2017. Mortality rate of clarias gariepinus fingerlings exposed to 2, 3-dichlorovinyl dimethyl phosphate. Journal of Applied Life Sciences International, pp.1-6.
[5] Eldahshan, O.A., 2015. Comparison of chemical and antimicrobial studies of Egyptian mandarin leaves and green branches volatile oil. European Journal of Medicinal Plants, pp.248-254.
