chiral. Such optical activity was described in adamantane in 1969 with the four different substituents being hydrogen, bromine and methyl and carboxyl group. The values of specific rotation are small and are usually within 1°. Nomenclature Using the rules of systematic nomenclature, adamantane is called tricyclo[3.3.1.13,7]decane. However, IUPAC recommends using the name "adamantane". The adamantane molecule is composed of only carbon and hydrogen and has Td symmetry. Therefore, its 16 hydrogen and 10 carbon atoms can be described by only two sites, which are labeled in the figure as 1 (4 equivalent sites) and 2 (6 equivalent sites). Structural relatives of adamantane are noradamantane and homoadamantane, which respectively contain one less and one more CH2 link than the adamantane. Chemical properties Adamantane cations The adamantane cation can be produced by treating 1-fluoro-adamantane with SbF5. Its stability is relatively high. The dication of 1,3-didehydroadamantane was obtained in solutions of superacids. It also has elevated stability due to the phenomenon called "three-dimensional aromaticity" or homoaromaticity. This four-center two-electron bond involves one pair of electrons delocalized among the four bridgehead atoms. Reactions Most reactions of adamantane occur via the 3-coordinated carbon sites. They are involved in the reaction of adamantane with concentrated sulfuric acid which produces adamantanone. The carbonyl group of adamantanone allows further reactions via the bridging site. For example, adamantanone is the starting compound for obtaining such derivatives of adamantane as 2-adamantanecarbonitrile and 2-methyl-adamantane. Bromination Adamantane readily reacts with various brominating agents, including molecular bromine. The composition and the ratio of the reaction products depend on the reaction conditions and especially the presence and type of catalysts. Boiling of adamantane with bromine results in a monosubstituted adamantane, 1-bromadamantane. Multiple substitution with bromine is achieved by adding a Lewis acid catalyst. The rate of bromination is accelerated upon addition of Lewis acids and is unchanged by irradiation or addition of free radicals. This indicates that the reaction occurs via an ionic mechanism. Fluorination The first fluorinations of adamantane were conducted using 1-hydroxyadamantane and 1-aminoadamantane as initial compounds. Later, fluorination was achieved starting from adamantane itself. In all these cases, reaction proceeded via formation of adamantane cation which then interacted with fluorinated nucleophiles. Fluorination of adamantane with gaseous fluorine has also been reported. Carboxylation Carboxylation of adamantane with formic acid gives 1-adamantanecarboxylic acid. Oxidation 1-Hydroxyadamantane is readily formed by hydrolysis of 1-bromadamantane in aqueous solution of acetone. It can also be produced by