Haworth conformational formulas of cyclic sugars

(redirected from envelope conformation)

Ha·worth con·for·ma·tion·al for·mu·las of cy·clic sug·ars

(hā'wŏrth),
for the pyranoses, these depict those shapes (conformations) on which no, one, or two ring-atoms lie outside the plane of the ring. If there are two such atoms para to each other, they can lie 1) on opposite sides of the plane (trans), giving chair forms, or 2) on the same side of the plane (cis), giving boat forms.
Similarly, there are six boat conformations. If the two (trans) exoplanar atoms are meta to each other, the conformation is a skew form; if the two atoms are ortho to each other, the conformation is a half-chair form.
For the furanoses, the envelope conformations have one ring-atom exoplanar. If there are three adjacent, coplanar ring-atoms (the two exoplanar ring-atoms on opposite sides of the plane), the conformations are twist forms.
[Sir Walter Norman Haworth]

Haworth,

Sir Walter Norman, English chemist and Nobel laureate, 1883-1950.
Haworth conformational formulas of cyclic sugars - for the pyranoses, these depict those shapes on which 0 to 2 ring-atoms lie outside the plane of the ring.
Haworth perspective formulas of cyclic sugars - these formulas depict the planar conformation, a situation not usually met.
References in periodicals archive ?
2001) have shown that in thiadiazine-2-thione ling shows an envelope conformation in which the N atom lies out of the plane while the rest of the atoms are co-planner.
The most important conformational changes that the given an envelope conformation can undergo are concerned with ring inversion, where N can be either above or below the mean plane, as well as the N inversion which leads to situation in which the substituents attached at N can be either in an axial or in equivatorical position