Structure and Isomerism
Galactose exists in both open-chain and cyclic form. The open-chain form has a carbonyl at the end of the chain. In the open-chain form D- and L- isomers cannot be separated, but the cyclic forms can be crystallized and isolated.
Four isomers are cyclic, two of them with a pyranose (six-membered) ring, two with a furanose (five-membered) ring. Galactofuranose occurs in bacteria, fungi and protozoa. In the cyclic form there are two anomers, named alpha and beta, since the transition from the open-chain form to the cyclic form involves the creation of a new stereocenter at the site of the open-chain carbonyl. In the beta form, the alcohol group is in the equatorial position, whereas in the alpha form, the alcohol group is in the axial position.
Read more about this topic: Galactose
Famous quotes containing the words structure and and/or structure:
“Science is intimately integrated with the whole social structure and cultural tradition. They mutually support one other—only in certain types of society can science flourish, and conversely without a continuous and healthy development and application of science such a society cannot function properly.”
—Talcott Parsons (1902–1979)
“Who says that fictions only and false hair
Become a verse? Is there in truth no beauty?
Is all good structure in a winding stair?
May no lines pass, except they do their duty
Not to a true, but painted chair?”
—George Herbert (1593–1633)