1,1-Diphenylindan was treated with one molecule of bromine. It yielded a monobromide, which was condensed with methyl and ethyl alcohols, piperidine, p-toluidine, and aniline. With aqueous solutions of potassium carbonate, the monobromide directly gave rise to 1,1-diphenylindene and small quantities of diphenylindanyl ether.The condensation of the monobromide with sodium ethyl malonate yielded ethyl 1,1-diphenyl-3-indanmalonate from which 1,1-diphenyl-3-indanmalonic and 1-1-diphenyl-3-indanacetic acids were prepared. A few derivatives of these acids were also obtained.To establish the constitution of 1,1-diphenyl-3-indanacetic acid and, hence, that of the monobromide and of the other compounds, this acid was prepared directly from 3,3-diphenyl-1-indanone by a Reformatsky reaction with ethyl bromoacetate.The method of preparation of 1,1-diphenylindan has been improved, 1,1-diphenylindene has been obtained by new methods, and the following compounds are described, as far as the authors are aware, for the first time: 3-bromo-1,1-diphenylindan, 3-methoxy-1,1-diphenylindan, 3-ethoxy-1,1-diphenylindan, 3-N-piperidyl-1,1-diphenylindan, N-phenyl-1,1-diphenyl-3-indanamine, N-p-tolyl-1,1-diphenyl-3-indanamine, ethyl 1,1-diphenyl-3-indanmalonate, 1,1-diphenyl-3-indanmalonic acid, 1,1-diphenyl-3-indanmalonic acid p-nitrobenzyl ester, silver salt of 1,1-diphenyl-3-indanmalonic acid, 1,1-diphenyl-3-indanacetic acid, 1,1-diphenyl-3-indanacetic acid p-nitrobenzyl ester, silver salt of 1,1-diphenyl-3-indanacetic acid, 1,1-diphenyl-3-indanacetanilide, 1,1-diphenyl-3-indanacetamide, 1,1-diphenyl-3-indanacetonitrile, 1,1-diphenyl-3-indanethylamine hydrochloride, ethyl 3-hydroxy-1,1-diphenyl-3-indanacetate, ethyl 1,1-diphenyl-3-indeneacetate, 1,1-diphenyl-3-indeneacetic acid, silver salt of 1,1-diphenyl-3-indeneacetic acid, 1,1-diphenyl-3-indeneacetic acid p-nitrobenzyl ester, ethyl 1,1-diphenyl-3-indanacetate.