Carbamate Salt Research Articles

Tin oxide surfaces. Part 4.—Infrared study of the adsorption of oxygen and carbon monoxide + oxygen mixtures on tin(IV) oxide, and the adsorption of carbon dioxide on ammonia-pretreated tin(IV) oxide

The transmission infrared technique has been used to study the adsorption of oxygen and carbon monoxide + oxygen mixtures on tin(IV) oxide. Adsorption of oxygen results in the appearance of two weak bands at 1155 and 1020 cm–1 which did not shift using 18O-enriched oxygen. No assignment of the species responsible for these bands was made, but the accompanying broad intense band below 900 cm–1 is associated with surface Sn—O—Sn bridges. Surface carbonate and bicarbonate species are formed slowly when the oxide is exposed to carbon monoxide + oxygen mixtures, essentially independent of the gas mixture composition in the range 10–70 % CO. No bulk reduction of the oxide was observed, in contrast to the behaviour previously observed with carbon monoxide alone. Hydration of the oxide surface prior to treatment with adsorbent severely inhibits the adsorption of carbon dioxide and carbon monoxide + oxygen mixtures. Preadsorbed ammonia has a similar inhibiting effect with carbon dioxide, but leads to the formation of a low stability carbamate salt of the unsubstituted carbamic acid, H2NCO2H.

Pentacarbonyliron-catalyzed carbonylation of amines to formamides

Carbon dioxide (CO2) was found to serve as a novel and green catalyst for the first time in N-formylation of amines with N, N-dimethylformamide (DMF), wherein only the aliphatic amines were applicable to afford the formamides in the yield of 71∼95%. The isotope labeling experiment with DMF-d7 indicated that the N-formyl group in the formylated product was originated from DMF rather than CO2. The control experiments and the in situ high-pressure FT-IR spectra demonstrated that the formation of the carbamate salt of cyclohexylammonium cyclohexylcarbamate (A) derived from the reaction of CO2 with cyclohexylamine was the driving force for this reaction. Accordingly, the mechanism of CO2-catalyed N-formylation of aliphatic amines with DMF was proposed, involving the formation of carbamate salt intermediate with enhanced nucleophilicity in anion in favor of the attack on carbonyl-group of DMF.

Carbamate Ions as Propagating Species in N-Carboxy Anhydride Polymerizations

Abstract Polymerizations of N-carboxy anhydrides of L-phenylalanine, γ-benzyl-L-glutamate, O-carbobenzoxy-L-tyrosine, L-leucine, and sarcosine, as initiated by primary, secondary, and tertiary amines in N2 or CO2 atmospheres and in the presence or absence of NaH, indicate that they proceed via carbamate salt intermediates. This conclusion is supported by radiotracer studies as well as by NMR studies of the initial products of NCA-amine reaction mixtures. The “activated monomer” mechanism of strong-base initiated polymerizations is discounted on the bases that polypeptides are not formed in aprotic tertiary amine-initiated systems (hydantoins and diketopiperazines are obtained instead) and that methoxyl end groups are detected in polypeptides initiated with 14C-labeled NaOCH3.

Enhancement of the optical rotation of α-amino-acids by formation of carbamate (N-carboxy-) salts

The optical rotations of fourteen L-α-amino acids dissolved in aqueous potassium carbonate became more positive with time, eventually reaching limiting, values, with optical activity enhancements ranging from <1 to >50 fold. The 1H n.m.r. signals from the α-protons showed a concomitant down-field shift. These changes are explained by the formation of carbamate (N-carboxy-) salts. The 13C n.m.r. spectra also altered with time, showing the gradual appearance of a signal assigned to the carbamate carbon atom.

The conversion of methyl 12‐ketostearate to 1, 12‐diisocyanatooctadecane

AbstractA method has been developed for the preparation of 1, 12‐diisocyanatooctadecane in good purity and overall yield of 42%. Methyl 12‐ketostearate is converted via the amide into 12‐ketostearonitrile and then by reductive amination into 1, 12‐diaminoctadecane. The corresponding diisocyanate was prepared by phosgenation of the diamine, its dihydrochloride or its carbamate salt. Variables in reaction conditions were examined to maximize yield and purity of these products.