Agar is a mixture of polysaccharides, not a single compound, and therefore does not have a single, definitive chemical formula. However, the approximate chemical formula for one of its main components, agarose, can be represented as (C12H18O9)n.
Agar is a complex mixture primarily composed of two polysaccharides: agarose and agaropectin. These components vary in structure and proportion depending on the source of the agar (typically red algae).
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Agarose: This is the major gelling component of agar. It is a neutral, non-ionic polysaccharide consisting of repeating units of β-D-galactopyranose and 3,6-anhydro-α-L-galactopyranose. The approximate formula (C12H18O9)n indicates a repeating unit 'n' times within the larger polymer structure.
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Agaropectin: This is a more complex mixture of smaller molecules that include sulfated polysaccharides. Due to its heterogeneous nature, a single chemical formula cannot accurately represent agaropectin.
Therefore, stating a single chemical formula for "agar" is misleading. While (C12H18O9)n provides a representation for the repeating unit of agarose, it does not encompass the entire composition of agar, which includes agaropectin and other minor components. The linked reference provided C14H24O9, this formula could potentially be referring to a specific fragment or a derivative of a component found within agar, but it's not a general formula for agar as a whole.
