Methods for producing 5-(halomethyl)furfural

A method for producing 5-(halomethyl)furfural, comprising:

• combining feedstock, aqueous acid, and halide salt to produce 5-(halomethyl)furfural,
• wherein the feedstock comprises one or more C6 monosaccharides, disaccharides comprising monomeric units having six carbon atoms, or polysaccharides comprising monomeric units having six carbon atoms;
• wherein the aqueous acid and the halide salt react to provide a halogen-containing mineral acid in situ;
• and
• wherein the combination of the feedstock, the aqueous acid, and the halide salt has a hydrogen concentration of less than or equal to 8 M, and a halide concentration of at least 8 M.