170
Henglein 1956) and by French’s group (Thoma and French 1959, 1960; James et al.
1959). The intensity at the absorption maximum was considerably changed with the
increase of α-cyclodextrin concentration. Professor Casu suggested that molecular
encapsulation was “an interesting tool to remove dyes from aqueous solution” (Casu
and Rava 1966).
In 1967, Professor Casu published the first perspective view of 2,6-di-O- methylated
cyclodextrin (Casu et al. 1967). When deuterium replaced a hydrogen- bonding proton, the resulting D-bond was weaker than the original H-bond if this H-bond was
strong, while the contrary was valid for weak H-bonds. The data showed that the
NMR signals of the corresponding hydroxyl groups occurred at field higher than that
of the O 2 -H/O 3 -H signals of amylose. The existence of an intramolecular H-bond was
strongly substantiated by the concentration and solvent independence of the NMR and
IR OH absorptions. However, this internal H-bond was not particularly strong. If it
was regarded as somewhat intermediate between the “strong” and the “weak” H-bond,
no substantial preferences of H of D were expected for the oxygen at C-3 of di-Omethylated cyclodextrins. Professor concluded that “more accurate results will certainly shed light on this facet in the near future when NMR instruments with higher
resolution and sensitivity will be available” (Casu et al. 1967).
Later, Professor Casu prepared cyclodextrin derivatives such as methylated
(Casu 1968a; Casu et al. 1968c) and acetylated (Casu et al. 1970) products. This
work was further supported by a grant from the US Department of Agriculture. The
Fig. 3.7 Relationship between the dissociation constants of substituted benzoic acids included in
α-cyclodextrin and the Hammett’s substituent constants proposed by Professor Casu in 1966.
(Source: Ronzoni Institute archives)
Fig. 3.8 Inclusion complex between methyl orange dye and α-cyclodextrin proposed by Professor
Casu in 1966. (Source: Ronzoni Institute archives)
G. Torri et al.
Henglein 1956) and by French’s group (Thoma and French 1959, 1960; James et al.
1959). The intensity at the absorption maximum was considerably changed with the
increase of α-cyclodextrin concentration. Professor Casu suggested that molecular
encapsulation was “an interesting tool to remove dyes from aqueous solution” (Casu
and Rava 1966).
In 1967, Professor Casu published the first perspective view of 2,6-di-O- methylated
cyclodextrin (Casu et al. 1967). When deuterium replaced a hydrogen- bonding proton, the resulting D-bond was weaker than the original H-bond if this H-bond was
strong, while the contrary was valid for weak H-bonds. The data showed that the
NMR signals of the corresponding hydroxyl groups occurred at field higher than that
of the O 2 -H/O 3 -H signals of amylose. The existence of an intramolecular H-bond was
strongly substantiated by the concentration and solvent independence of the NMR and
IR OH absorptions. However, this internal H-bond was not particularly strong. If it
was regarded as somewhat intermediate between the “strong” and the “weak” H-bond,
no substantial preferences of H of D were expected for the oxygen at C-3 of di-Omethylated cyclodextrins. Professor concluded that “more accurate results will certainly shed light on this facet in the near future when NMR instruments with higher
resolution and sensitivity will be available” (Casu et al. 1967).
Later, Professor Casu prepared cyclodextrin derivatives such as methylated
(Casu 1968a; Casu et al. 1968c) and acetylated (Casu et al. 1970) products. This
work was further supported by a grant from the US Department of Agriculture. The
Fig. 3.7 Relationship between the dissociation constants of substituted benzoic acids included in
α-cyclodextrin and the Hammett’s substituent constants proposed by Professor Casu in 1966.
(Source: Ronzoni Institute archives)
Fig. 3.8 Inclusion complex between methyl orange dye and α-cyclodextrin proposed by Professor
Casu in 1966. (Source: Ronzoni Institute archives)
G. Torri et al.