Thiamine (vitamin B1; the old name is aneurin) is an organic heterocyclic compound, a water-soluble vitamin. When the metabolism of thiamine is disturbed, a disorder in the oxidative decarboxylation of α-keto acids first occurs and the metabolism of carbohydrates is partially blocked. The thiamine molecule contains two methylene-bonded rings: pyrimidine and thiazole. Thiamine bromide (vitamin B1) is a derivative of heterocyclic compounds: