When dehydrogenate some pentose like arabinose for example with diluted H2SO4 in heatin the process of formation furfurol is less revirsible than when using hexose sourse and the the formed w-oximethyl -furfurol which is soluble in water for diference with furfurol and it cant be steamed and it also destroy in hot acidic media giving HCOOH and levulinic acid.