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The carbons of the chain are conventionally numbered from 1 to n, starting from the end which is closest to the carbonyl. If the carbonyl is at the very beginning of the chain (carbon 1), the monosaccharide is said to be an aldose, otherwise it is a ketose. These names can be combined with the chain length prefix, as in aldohexose or ...
A open-chain form of glucose makes up less than 0.02% of the glucose molecules in an aqueous solution at equilibrium. [58] The rest is one of two cyclic hemiacetal forms. In its open-chain form, the glucose molecule has an open (as opposed to cyclic) unbranched backbone of six carbon atoms, where C-1 is part of an aldehyde group H(C=O)−.
Numbering of the chain. This is done by first numbering the chain in both directions (left to right and right to left), and then choosing the numbering which follows these rules, in order of precedence. Not every rule will apply to every compound, rules can be skipped if they do not apply. Has the lowest-numbered locant (or locants) for ...
Skeletal structural formula of Vitamin B 12.Many organic molecules are too complicated to be specified by a molecular formula.. The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are connected to one another. [1]
The number of distinct stereoisomers with the same diagram is bounded by 2 c, where c is the total number of chiral carbons. The Fischer projection is a systematic way of drawing the skeletal formula of an acyclic monosaccharide so that the handedness of each chiral carbon is well specified.
The conventional numbering of the carbons in the closed form is the same as in the open-chain form. If the sugar is an aldohexose, with the carbonyl in position 1, the reaction may involve the hydroxyl on carbon 4 or carbon 5, creating a hemiacetal with five- or six-membered ring, respectively.
Fischer projections are commonly constructed beginning with a sawhorse representation. To do so, all attachments to main chain carbons must be rotated such that resulting Newman projections show an eclipsed configuration. [2] The carbon chain is then positioned vertically upward with all horizontal attachments pointing toward the viewer. [2]
Now the position of the oxygen atom can be defined as on carbon atom number two, three or four. However, atoms two and four are exactly equivalent - which can be shown by turning the molecule around by 180 degrees. The locant is the number of the carbon atom to which the oxygen atom is bonded.