Acetoxy-γ-valerolactone

Levulinyl cellulose esters have been produced as an effective renewable binder for architectural coatings. The title compound, C7H10O4 (systematic name: 2-methyl-5-oxotetrahydrofuran-2-yl acetate), assigned as the esterifying species, was isolated and crystallized to confirm the structure. In the crystal, the molecules pack in layers parallel to (102) utilizing weak C—H⋯O interactions.

Levulinyl cellulose esters have been produced as an effective renewable binder for architectural coatings. The title compound, C 7 H 10 O 4 (systematic name: 2-methyl-5-oxotetrahydrofuran-2-yl acetate), assigned as the esterifying species, was isolated and crystallized to confirm the structure. In the crystal, the molecules pack in layers parallel to (102) utilizing weak C-HÁ Á ÁO interactions.

Comment
Acetoxy-γ-valerolactone (2-methyl-5-oxotetrahydrofuran-2-yl acetate) was first described by Bredt (1886) and became of interest during our investigation of novel, renewable levulinyl cellulose esters. Esterification of cellulose in the presence of levulinic acid and an aliphatic anhydride affords a mixed cellulose levulinyl ester which we have shown has particular utility in architectural coatings [Glenny et al., 2012]. Levulinyl acetyl cellulose was generated by the sulfuric acid catalysed esterification of cellulose in the presence of acetic anhydride and levulinic acid. Analysis of this reaction mixture indicated that a valero-lactone species predominated rather than the anticipated mixture of anhydrides.
Acetoxy-γ-valerolactone was isolated by flash chromatography and identified as the major species in the reaction solution and has been assigned as the esterifying reagent. The generation of acetoxy-γ-valerolactone from acetic anhydride and levulinic acid had previously been reported (Rasmussen & Brattain, 1949) and also had been shown to be an esterifying agent forming levulinyl and acetyl amides (Suami & Day, 1959). When isolated in our hands, acetoxy-γvalerolactone remained as a super cooled liquid, much like levulinic acid which exists as a light yellow solid or liquid, but will crystalize and displays a melting point between 30-33°C. Bell and Covington (1975) described the material as a solid with a melting point between 75-76°C but without supporting crystal structure data. The molecule was therefore crystallized from DCM and petroleum ether and the crystal structure elucidated. This confirmed the molecular structure and assisted with investigation into its esterification chemistry.
The title compound, C 7 H 10 O 4 , crystallizes with one unique molecule per asymetric unit. The five-membered ring adopts a flattened envelope conformation with O1 atom as a flap which deviates by 0.128 (1) Å from the mean plane P formed by the four C atoms. The acetate fragment is oriented in such a way that its mean plane and plane P are almost perpendicular to each other with an interplanar angle of 83.18 (7)°. There are no closely related structures in the Cambridge Structural Database, the closest being 5-(1-adamantyl)-5-ethoxytetrahydrofuran-2-one, LAGQUG (Cai et al., 2004).
In the crystal, weak C methyl -H···O acetate hydrogen bonds link the molecules into centrosymmetric dimers with the well known R 2 2 (8) motif (Bernstein et al., 1995), and weak C methylene -H···O ketone interactions (Table 1) link further these dimers into layers parallel to (102). Table 1.

Refinement
All methyl H atoms were constrained to an ideal geometry (C-H = 0.98 Å) with U iso (H) = 1.5U eq (C), but were allowed to rotate freely about the adjacent C-C bond. All other C bound H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with C-H distances of 0.99 Å and with U iso (H) = 1.2U eq (C).

Figure 1
ORTEP (Farrugia, 2012) view of the title molecule showing the atomic numbering and 50% probability displacement ellipsoids.