1,147,541. Substituted imidazolidines and imidazolines; cholesterol ester. E. I. DUPONT DE NEMOURS &amp; CO. 7 March, 1966 [12 March, 1965; 3 June, 1965; 9 Feb., 1966], No. 9931/66. Headings C2C and C2U. [Also in Divisions A5, C3, C4 and C5] Novel imidazolidines and imidazolines of the respective formulµ wherein R represents hydrogen, hydrocarbyl or hydrocarbyl substituted with at least one of the following up to 6 fluorine, chlorine and bromine atoms; OH; NH 2 ; hydrocarbyloxy; hydrocarbylamino; or hydrocarbylamino or hydrocarbyloxy containing oxygen or nitrogen in the hydrocarbon chain and/or substituted by OH, NH 2 , COOH, COOM or F, C1 or Br (M is alkali metal or the equivalent of an alkaline earth metal), X represents any of the possibilities defined for R or RCO- or ROCO- (R having the above significance), Z, Z&lt;SP&gt;1&lt;/SP&gt;, Z&lt;SP&gt;2&lt;/SP&gt; and Z&lt;SP&gt;3&lt;/SP&gt; represent hydrogen or fluorine and may be the same or different, with the proviso that R and X together contain no more than 30 carbon atoms (the term &#34;hydrocarbyl&#34; means the radical derived from a hydrocarbon and includes alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl, alkaryl and aralkyl radicals and the hydrocarbylamino group may constitute a heterocyclic ring based on the nitrogen atom while the oxygen or nitrogen is a hydrocarbyl chain may be the hetero-atom of a heterocyclic ring, are prepared in the case where R is H and X is polyfluoromethylethylamino by reacting an alkali metal cyanide with one polyfluoroalkylideneimine of the formula Z and Z&lt;SP&gt;1&lt;/SP&gt; having the above significance, where a compound is required having Z&lt;SP&gt;2&lt;/SP&gt; and Z&lt;SP&gt;3&lt;/SP&gt; respectively identical with Z and Z&lt;SP&gt;1&lt;/SP&gt;, or by reacting the said cyanide with more than one such polyalkylideneimine where a compound is required having Z&lt;SP&gt;2&lt;/SP&gt; and/or Z&lt;SP&gt;3&lt;/SP&gt; different from Z and Z&lt;SP&gt;1&lt;/SP&gt;, under conditions which avoid elimination of the polyfluoromethylethylamino substituent; in the case where R and X are hydrogen, by carrying out the previous process to form the compound in which X is polyfluoromethylethylamino and eliminating this substituent, by heating, for example in the presence of mineral acid; in the case where R and/or X is other than hydrogen by reacting the compound prepared by the previous process with a hydrocarbylating, substituted hydrocarbylating or acylating agent (in reaction with oxalyl chloride a 4-isocyanato compound is formed which may then be either reduced to form a compound where R is hydrogen and X is methyl or an alcohol or amino-alcohol to form a 4-carbalkoxyimino or 4-aminoalkoxycarbonylimino compound). Any compound of the above formula in which R is hydrogen or R and X are both hydrogen may be reacted with the appropriate hydrocarbylating or acylating agent. Such reactions including the Mannich reaction using formaldehyde and an amine to introduce an aminomethyl substituent, and the reaction with formaldehyde to introduce a hydroxyalkoxy substituent. Compounds of the above formula in which R or X contain an amino group form salts with acids or quaternary ammonium salts. Compounds in which R represents hydrogen exhibit acidic properties and form salts with bases, e.g. alkali metal salts may be formed. One of the novel comcompounds is a cholesterol ester of the formula and is prepared by reacting 4-isocyanato-2,2,5,5- tetrakis (trifluoromethyl) - 3 - imidazoline and cholesterol. Pentafluoroisopropylideneimine is prepared by reacting phenyl isocyanate and pentafluoroacetone in the presence of triphenylphosphine and treating the resulting N-phenylpentafluoroisopropylideneimine with ammonia and then phosphorus pentoxide.