Staggered-anti

Typical carbon-oxygen bond distances m ethers are similar to those of alcohols (—142 pm) and are shorter than carbon-carbon bond distances m alkanes (—153 pm) An ether oxygen affects the conformation of a molecule m much the same way that a CH2 unit does The most stable conformation of diethyl ether is the all staggered anti conformation Tetrahydropyran is most stable m the chair conformation—a fact that has an important bearing on the structures of many carbohydrates... 

The Karplus equation predicts that J is largest when the two CH bonds are staggered anti (0=180") or eclipsed (0=0°), and J is smallest when the two bonds are perpendicular (0=90"). Because of J s dependence on dihedral angle, it can be used to distinguish between isomers such as artemisin acetate and 6-epiartemisin acetate. 

Alkane conformations can be classified as eclipsed, staggered, anti, or gauche depending on the relative orientation of the groups on adjacent carbons. 

A large variety of situation is encountered. Some compounds follow the vinyl alcohol, with two planar conformations, and a more stable syn than anti (see for instance curve for cis CHBr=CHOH - 17 in fig. 6 ). In some other, a planar anti conformation is the more stable (for instance CH2=CBrOH - 18 in fig. 6). In a number of compounds, the anti form is more or less staggered (for instance CC12=CHSH - 34 in fig. 8). There might even be neither syn nor anti planar conformations, but only a staggered anti one (for instance C2F3SH - 30 in fig. 

Figure 19.14 Panel A shows dopamine, 13 from prior Scheme 19.7, in its extended or (E) conformation, which allows for a staggered anti-Newman Projection formula (Ar = 3,4-dihydroxyphenyl). Panel B shows 13 in its folded or (F) conformation, which leads to a fully eclipsed Newman Projection formula of higher energy. Panel C shows ADTN 29, THiQ 30 and apomor-phine 31. d1, d2, d1 and d2 (in the far-right column) refer to distances between the partners for groups (a), (b), and (c) that would exist on the dopamine receptor in order to accommodate dopamine s E or F conformation, respectively. The different spatial arrangements for these two sets of partnering groups are apparent.

The carbon-carbon single bonds of saturated fatty acid alkyl chains exist largely in the staggered, anti conformation, meaning they can pack together relatively well, and are held together by dispersion forces (Section 2.7A). As a result, both saturated fatty acids and... 

Saturated fatty add alkyl chains in the staggered, anti conJformation... 

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