# What is the compound formula on for sugar?

Aug 7, 2017

There are a lot of sugars...

#### Explanation:

We can separate sugars into groups based on their empirical formula.

Monosaccharides, the simplest type of carbohydrates, are sugars that cannot hydrolyze to give simpler sugars, and that have the general chemical formula

${\text{C"_n"H"_(2n)"O}}_{n}$

where $n$ is a positive integer

Some examples of monosaccharides include glucose , fructose, galactose (all share formula ${\text{C"_6"H"_12"O}}_{6}$) ribose, lyxose, and xylose (all share formula ${\text{C"_5"H"_10"O}}_{5}$)

Disaccharides are sugars that consist of two monosaccharides joined together via glycosidic bonds. All disaccharides have the formula

${\text{C"_12"H"_22"O}}_{11}$

The most common example is sucrose, common table sugar. Other sugars such as lactose and maltose are also disaccharides, and have the same chemical formula.

Polysaccharides are long chains of monosaccharides joined by glycosidic linkage. The typical general formula is

${\text{C"_x"(H"_2"O)}}_{y}$

where $x$ is generally large, usually in the range of $200 - 2500$.

The formula simplifies to

${\text{C"_(6n)"H"_(10n)"O}}_{5 n}$

if the repeating units in the polymer backbone are six-carbon monosaccharides (such as glucose).

There is a fourth carbohydrate group, called the oligosaccharides, for which there is no general formula. These sugars consist of usually $3 - 10$ linked monosaccharides.

A general rule of thumb is given below regarding the number of monosaccharides within the compound:

if the number of monosaccharides is $2$, it is a disaccharide

if the number of monosaccharides is $3 - 10$, it is an oligosaccharide

if the number of monosaccharides is $10 +$, it is a polysaccharide