Staggered conformer

In the staggered conformation each C—H bond of one carbon bisects an H—C—H angle of the other carbon... 

FIGURE 3 2 Some commonly used draw mgs of the staggered conformation of ethane... 

Eclipsed bonds are characterized by a torsion angle of 0° When the torsion angle is approximately 60° we say that the spatial relationship is gauche, and when it is 180° we say that it is anti Staggered conformations have only gauche or anti relationships between bonds on adjacent atoms... 

Of the two conformations of ethane the staggered is 12 kJImol (2 9 heal mol) more stable than the eclipsed The staggered conformation is the most stable conformation the eclipsed is the least stable conformation Two main explanations have been offered for the difference in stability between the two conformations One explanation holds that repulsions between bonds on adjacent atoms destabilize the eclipsed conformation The other suggests that better electron delocalization stabilizes the staggered conformation The latter of these two explanations is now believed to be the correct one... 

At any instant almost all of the molecules are in staggered conformations hardly any are in eclipsed conformations... 

Rotation around carbon-carbon bonds is one of the fastest processes m chemistry Among the ways that we can describe the rate of a process is by its half life which is the length of time it takes for one half of the molecules to react It takes less than 10 s for half of the molecules m a sample of ethane to go from one staggered conformation to another at 25°C... 

Figure 3 7 illustrates the potential energy relationships among the various confer matrons of butane The staggered conformations are more stable than the eclipsed At any instant almost all the molecules exist m staggered conformations and more are present m the anti conformation than m the gauche The point of maximum potential... 

It IS no accident that sections of our chair cyclohexane drawings resemble saw horse projections of staggered conformations of alkanes The same spatial relationships seen m alkanes carry over to substituents on a six membered ring In the structure... 

Section 3 1 The most stable conformation of ethane is the staggered conformation It IS approximately 12 kJ/mol (3 kcal/mol) more stable than the eclipsed, which IS the least stable conformation... 

Staggered conformation of ethane (most stable conformation)... 

Section 3 2 The two staggered conformations of butane are not equivalent The anti conformation is more stable than the gauche... 

Like hydrogen peroxide the inorganic substances hydrazine (H2NNH2) and hydroxylamine (H2NOH) possess conformational mobility Wnte stmctural representations or build molecular models of two different staggered conformations of (a) hydrazine and (b) hydroxylamine... 

One of the staggered conformations of 2 methylbutane in Problem 3 17b is more stable than the other Which one is more stable" Why" ... 

Compare the two staggered conformations of 1 1 2 2 tetrafluoroethane on Learning By Mod elmg Do they differ in respect to their dipole moments How" ... 

FIGURE 7 9 Repre sentations of (2/ 3R) dihy droxybutanoic acid (a) The staggered conformation is the most stable but is not properly arranged to show stereochemistry as a Fischer projection (b) Rotation about the C 2-C 3 bond gives the eclipsed conforma tion and projection of the eclipsed conformation onto the page gives (c) a correct Fischer projection... 

Construct a molecular model corresponding to the Fischer projection of rneso 2 3 dibro mobutane Convert this molecular model to a staggered conformation in which the bromines are anti to one another Are the methyl groups anti or gauche to one another in this staggered con formation" ... 

Red circles gauche 60° and 300° Red circles anti 180° Gauche and anti relationships occur only in staggered conformations therefore ignore the eclipsed conformations (0° 120° 240° 360°)... 

The three staggered conformations are different for valine because the three groups attached to Cp are different. The first staggered conformation (b) is less crowded and energetically most favored because the two methyl groups bound to Cp are both close to the small H atom bound to Ca-... 

Ethyl dibromodihydrocinnamate (14), for example, can form the three staggered conformers 14a-c by rotation around the CC single bond a to the phenyl ring. 

One of the frmdamental structural facets of organic chemistry, which has been explained most satisfactorily in MO terms, is the existence of a small barrier to rotation about single bonds. In ethane, for example, it is known that the staggered conformation is about 3kcal/mol more stable than the ecl sed conformation so that the eclipsed conformation represents a transition state for transformation of one staggered conformation into another by rotation. 

Ab initio MO calculations using 4-3IG orbitals indicate that the eclipsed conformation of acetaldehyde is more stable than the staggered conformation. 

Since the main chain in this representation is in an entirely staggered conformation, whereas in the Fischer projection formulas the conformation represented is completefy eclipsed, an anti relationsh between two adjacent substituents in an extended structure corresponds to being on the same side in a Fischer projection formula (erythro) whereas a syn relationship corresponds to being on opposite sides in die Fischer projection (three). 

Center of symmetry in anti staggered conformation of meso-tartaric acid... 

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