Hybrid shape

A more detailed comparison of the various carbon bonding hybrids in these species is presented in Fig. 3.12. This figure shows that the visual changes in hybrid shape, even for rather large changes in k (e.g., the changes from sp1 -like to sp3-like in the left-hand panels), are rather subtle. Most obvious is the increasing... 

Number of Electron Pairs at Central Atom Hybridization Shape of ... 

The latest embodiment of an SMP clot retrieval system demonstrates a hybrid shape-memory material system. The design of SMP biomedical devices should not be limited to purely polymer-based devices but rather can be combined with other smart or active materials. Novel multifunctional SMP-hybrid systems could lead to multiple unique and novel platform technologies for future development. 

FIGURE 2 Hybrid shape-memory materials approach to reconfigurable stmetures. a. Shape-memory tendons actuate a variably stiff shape-memory polymer beam that can be flexed with low-input energy, b. Upon cooling, the beam becomes stiff, locking shape deformations in place to handle exterior loads (here 500 g). 

When elements in Period 2 form covalent bonds, the 2s and 2p orbitals can be mixed or hybridised to form new, hybrid orbitals each of which has. effectively, a single-pear shape, well suited for overlap with the orbital of another atom. Taking carbon as an example the four orbitals 2s.2p.2p.2p can all be mixed to form four new hybrid orbitals (called sp because they are formed from one s and three p) these new orbitals appear as in Figure 2.9. i.e. they... 

Of the two extremes experimental studies indicate that the planar sp model describes the bonding m alkyl radicals better than the pyramidal sp model Methyl rad ical IS planar and more highly substituted radicals such as tert butyl radical are flattened pyramids closer m shape to that expected for sp hybridized carbon than for sp ... 

Section 16 2 The oxygen atom m an ether or epoxide affects the shape of the mole cule in much the same way as an sp hybridized carbon of an alkane or cycloalkane... 

Of the various geometric parameters associated with molecular shape, the one most nearly constant from molecule to molecule and most nearly independent of substituent effects is bond length. Bond lengths to carbon depend strongly on the hybridization of the carbon involved but are little influenced by other factors. Table 1.2 lists the interatomic distances for some of the most common bonds in organic molecules. The near constancy of bond lengths from molecule to molecule reflects the fact that the properties of individual bonds are, to a good approximation, independent of the remainder of the molecule. 

The shapes of the monomeric molecules of the Group 2 halides (gas phase or matrix isolation) pose some interesting problems for those who are content with simple theories of bonding and molecular geometry. Thus, as expected on the basis of either sp hybridization or the... 

The concept of hybridization explains how carbon forms four equivalent tetrahedral bonds but not why it does so. The shape of the hybrid orbital suggests the answer. When an 5 orbital hybridizes rvith three p orbitals, the resultant sp3 hybrid orbitals are unsyimmetrical about the nucleus. One of the two... 

What is the shape of benzene, and what hybridization do you expect for each carbon ... 

Allerie, P12C — C = CH2> is somewhat unusual in that it has two adjacent double bonds. Draw a picture showing the orbitals involved in the u and -n- bonds of allene. Is the central carbon atom sp2- or sp-hybridized What about the hybridization of the terminal carbons What shape do you predict for allene ... 

We saw in the last chapter how covalent bonds between atoms are described, and we looked at the valence bond model, which uses hybrid orbitals to account for the observed shapes of organic molecules. Before going on to a systematic study of organic chemistry, however, we still need to review a few fundamental topics. In particular, we need to look more closely at how electrons are distributed in covalent bonds and at some of the consequences that arise when the electrons in a bond are not shared equally between atoms. 

What kind of hybridization must the central carbon have Sketch the bonding it orbitals in allene. What shape do you predict for allene ... 

Further evidence for the unusual nature of benzene is that all its carbon-carbon bonds have the same length—139 pm—intermediate between typical single (154 pm) and double (134 pm) bonds. In addition, an electrostatic potential map shows that the electron density in all six carbon-carbon bonds is identical. Thus, benzene is a planar molecule with the shape of a regular hexagon. All C-C—C bond angles are 120°, all six carbon atoms are sp2-hybridized. and each carbon has a p orbital perpendicular to the plane of the six-membered ring. 

When there is more than one central atom in a molecule, we concentrate on each atom in turn and match the hybridization of each atom to the shape at that atom predicted by VSEPR. For example, in ethane, C2H6 (38), the two carbon atoms are both central atoms. According to the VSEPR model, the four electron pairs around each carbon atom take up a tetrahedral arrangement. This arrangement suggests sp hybridization of the carbon atoms, as shown in Fig. 3.14. Each... 

The promotion of electrons will occur if, overall, it leads to a lowering of energy by permitting the formation of more bonds. Hybrid orbitals are constructed on an atom to reproduce the electron arrangement characteristic of the experimentally determined shape of a molecule. 

FIGURE 3.16 Three common hybridization schemes shown as outlines of the amplitude of the wavefunction and in terms of the orientations of the hybrid orbitals, (a) An s-orbital and a p-orbital hybridize into two sp hybrid orbitals that >oint in opposite direc tions, forming a linear molecular shape, (b) An s-orbital and two p-orbitals can blend together to give three ip hybrid orbitals that point to the corners of an equilateral triangle, (c) An s-orbital and three p-orbitals can blend together to give four sp hybrid orbitals that point to the corners of a tetrahedron. 

---