3,6-Di- tert-butyl- o-benzosemiquinone is very convenient for the investigation of the interaction between organometallic R 2M and carbonyl compounds. The reaction of organometallic compounds R 2M with o-quinone, where R = Ph, Me, Et, Pr, 1Pr or tBu and M ≡ Zn, Cd, and Al, proceeds in two ways: (1) the single-electron oxidation of the organometallic compound by o-quinone, resulting in derivatives of alkyl(phenyl)oxyphenols; (2) the polar 1,2 and 1,4 addition of organometallic molecules to o-quinone as to conjugated ketone, which produces hydroxycyclohexadienones after hydrolysis. The relationship between these two is defined by the nature of the organometallic compound. The products of polar addition are rearranged easily in different ways, finally resulting in new o-quinones: 3-(R)-6- tert-butyl- o-benzoquinones and 3,6-di- tert-butyl-4-(R)- o-benzoquinones where R ≡ alkyl.