No abstract

No abstract

No abstract

No abstract

Precision data on heats of combustion of aliphatic aldehydes are lacking in the literature and since the appearance of Kharasch's compilation 1 no further determinations have heen puhlished. Therefore it was judged of interest to study a numher of aliphatic aldehydes. The choice of compounds was mainly governed by an interest in the aldol condensation reaction and associated processes for hutanaL SAMPLE PURITYIt is a well-known fact that simple aliphatic aldehydes are difficult to ohtain in a very pure state and this work has given no evidence for expressing an opposite opinion. Before descrihing the special prohlems met with in handling the aldehydes, the general procedure for preparing the samples for comhustion will he given. ProcedureAll six suhstances used in this investigation were prepared and carefully purified hy the Research Lahoratory, Mo and Domsjö Aktieholag, Örnsköldsvik, Sweden. After the final distillation in a Podhielniak column with 50-70 theoretical plates, samples of the main fraction were enclosed in sealed Pyrex-glass ampoules in an atmosphere of nitrogen or helium. On the contents of one of these ampoules the purity was estahlished using gas-liquid chromatography, and a numher of ampoules were sent without delay to our lahoratory. Immediately upon arrival (2-3 days later) a distillation was performed at room temperature under reduced pressure. All samples were handled in a nitrogen atmosphere and utmost care was taken to exclude air. The middle fraction from this distillation (ahout one-third of the total sample) was collected in a receiver where some ten combustion ampoules (made from soft glass) had heen placed in advance, and these were immediately sealed 2 • At the same time ampoules were filled with samples for gas-liquid chromatographic analysis and for density determination. The comhustions were made as soon as possible, and in no case more than six days elapsed hetween ampoule filling and the last comhustion. In the case of hutanal all experiments were carried out within two days. Analysis (by Mo and Domsjö) and density determination were performed so as to coincide in time with the middle experiment in the combustion series.The gas-liquid Chromatographieanalysis was clone in order to determine the amount of impurities, especially water. For all suhstances except hutanal the area under the water peak on the chromatogram was pro-*Published in Acta Chem. Scand., 14, 180 (1960) 129 Unauthenticated Download Date | 5/10/18 2:40 PM JAN TJEBBES portianal to the water content of the sample, which was found from calihration experiments with known amounts of water added to the sample. The linearity implies that no reaction leading to the formation of water occurred on the column. In the case of hutanal, however, a reaction took place on the column with formation of water.The water content of the hutanal sample was evaluated using the ohservation that the density of a sample of this compound varied linearly with the water content, at least over a small range. A sample of hutanal was prepar...