Dipropyl carbonate

Many esteis of carbonic acid are known, e.g.. diethyl carbonate, ethyl ester of metacarbonic acid, (C HjO) CO. made by reaclion of ethyl alcohol and carbonyl chloride dimethyl carbonate. (CH Oi CO. methyl ethyl carbonate, ethyl ester of orthocarbonic acid, (CyHxO C. bp 158°C. 

Hydrogens on carbon next to an ether oxygen are shifted downfield from the normal alkane resonance and show U-f NMR absorptions in the region 3.4 to 4.5 8. This downfield shift is clearly seen in the spectrum of dipropyl ether shown in Figure 18.4. 

Figure 18.4 The 1H NMR spectrum of dipropyl ether. Protons on carbon next to oxygen are shifted downfield to 3.4 S.

The l3C CP MAS spectra of the sample-A show the presence of the most prominent peak at 27.2 ppm for Ci carbon atom adjacent to the SH group and C2 carbon atom of the 3-mercaptopropyl group. There was another minor intensity broad peak at around 22.3 ppm which is assigned to C and C2 carbon atoms of the dipropyl disulfide. The presence of dipropyl disulfide in the sample A may be due to oxidative dehydrogenation of two adjacent thiol groups leading to the formation of disulfide (S-S) group. An unresolved shoulder down field to the C3 carbon of the thiol was observed for the C3 carbon of the dipropyl disulfide. Similar results were obtained by Lim et al. [6],... 

The oxidation of oximes offers an attractively simple route to nitroalkanes from carbonyl compounds. The most effective reagent is pertrifluoroacetic acid in acetonitrile in the presence of sodium hydrogen carbonate as a buffer. Yields are improved by the addition of small quantities of urea to remove oxides of nitrogen. The reaction is illustrated by the conversion of dipropyl ketoxime into 4-nitroheptane (Expt 5.190). 

Nitroheptane. Prepare a solution of pertrifluoroacetic acid in acetonitrile as follows. Place 50 ml of acetonitrile in a two-necked, 250-ml round-bottomed flask fitted with a dropping funnel and a reflux condenser. Insert a plastic-covered magnetic stirrer follower bar and cool the flask in an ice bath sited on the stirrer unit. To the cooled and stirred solution add 5.8 ml (0.2 mol) of 85 per cent hydrogen peroxide (1) and then 39.0 ml (58.1 g, 0.24 mol) of trifluoroacetic anhydride. Stir the solution for 5 minutes and then allow to warm to room temperature. In a three-necked, 500-ml round-bottomed flask fitted with a sealed stirrer unit, dropping funnel and reflux condenser place 200 ml of acetonitrile, 47 g (0.56 mol) of sodium hydrogen carbonate, 2g of urea and 12.9g (0.1 mol) of dipropyl ketoxime. Heat the stirred suspension under reflux on the water bath and add dropwise over 90 minutes the prepared solution of pertrifluoroacetic acid. When the addition is complete heat the mixture under reflux for 1 hour. Pour the cooled reaction mixture into 600 ml of cold water and extract with four 100 ml portions of dichloromethane (note the organic layer is the upper layer in the first extraction, but subsequently it is the lower layer). Wash the combined extracts with... 

Compounds which dissolve in concentrated sulphuric acid may be further classified as those which are soluble in syrupy phosphoric acid and those which are insoluble in this solvent in general dissolution takes place without the production of appreciable heat or colour. Those compounds soluble in phosphoric acid include alcohols, esters, aldehydes, methyl ketones and cyclic ketones provided that they contain less than nine carbon atoms. The solubility limit is somewhat lower than this for ethers thus dipropyl ether dissolves in 85 per cent phosphoric acid but dibutyl ether and anisole do not. Ethyl benzoate and diethyl malonate are insoluble. 

---