Предмет: Химия, автор: gkhudyshev

С помощью каких реактивов можно определить, в какой из трѐх выданных вам
пробирок находится крахмал, фруктоза, глюкоза? Как вы их отличите, что
будете наблюдать в каждом случае? Опишите кратко ход эксперимента
(уравнения писать не нужно).

Ответы

Автор ответа: azamatdzucev36

Ответ:

Как и все альдегиды, глюкоза легко окисляется. Она восстанавливает серебро из аммиачного раствора оксида серебра и медь (II) до меди (I). То есть проявляет восстановительные свойства. В частности в реакции растворов сульфата меди с глюкозой и гидроксидом натрия. При нагревании эта смесь реагирует с обесцвечением (сульфат меди сине-голубой) и образованием красного осадка оксида меди (I). Глюкоза при этом окисляется до глюконовой кислоты.

C6H12O6 + Ag2O → C6H12O7 + 2Ag↓

СН2ОН-(СНОН) 4-СОН + Сu(ОН) 2 →СН2ОН – (СНОН) 4 – СООН + Сu2О↓+ Н2О

Во фруктозе нет альдегидной группы, это - невосстанавливающий сахар, и она не даст этой реакции. С гидроксидом меди она, как и все многоатомные спирты дает комплекс темно-синего цвета

Крахмал йодом, раствор посинеет.

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