Orbital hybridization lone pair

While the present discussions focus on orbital hybridization relative to bonds between atoms, it is important to recognize that nonbonding electron pairs (lone pairs) also participate in orbital hybridization. Thus, as illustrated in Figure 5.4 and relating to. sp3-hybridized centers, for the purposes of determining orbital hybridization, lone pairs can be treated as bonds between a central atom and nothing. 

An orbital hybridization description of bonding in methylamine is shown in Figure 22.2. Nitrogen and carbon are both s/r -hybridized and are joined by a a bond. The unshared electron pair on nitrogen occupies an s/r -hybridized orbital. This lone pair-is involved in reactions in which fflnines act as bases or nucleophiles. The graphic that opened this chapter is an electrostatic potential map that clearly shows the concentration of electron density at nitrogen in rnethylanine. 

In our subsequent discussions, we shall be using consistently hybrid lone pair AO s and hybrid bond MO s. The explicit forms of these orbitals are given below, for the case of any lone pair, located on atom Y, and the case of an X—H bond ... 

Gas-Phase Spectroscopy. The 336-nm absorption band of triplet imidogen was first observed by Eder in 1892 and has been the subject of numerous subsequent studies. The singlet state of NH absorbs at 324 nm. The CASSCF (6,5)/ CASPT2 level of theory predicts transitions at 323 and 293 nm for singlet and triplet imidogen, respectively. In each spin state, an electron is promoted from the sp hybrid lone pair to a singly occupied 2p orbital as shown below for NH. 

Overlap of atomic orbitals (AO s) or hybrids allows electrons to pair up, forming a chemical bond hybrid orbitals valence AO s mix to accommodate "equivalent" bonded neighbors. Non-hybridized orbitals form lone pairs or n bonds. 

Thus the central iodine is dsp3 hybridized. Three of these hybrid orbitals hold lone pairs, and two of them overlap with sp3 orbitals from the other two iodine atoms to form cr bonds. 

How is the nitrogen atom of the pyridine ring hybridized The N atom is surrounded by three groups (two atoms and a lone electron pair), making it sp hybridized, and leaving one unhybridized p orbital with one electron that overlaps with adjacent p orbitals. The lone pair on N resides in an sp hybrid orbital that is perpendicular to the delocalized n electrons. 

An important outgrowth of this electronic configuration of bismuth is that trivalent bismuthines exhibit little basicity [94JCS(P1)3479]. The lack of basicity is due to the high s-character of the lone pair electron. All three valence electrons and two lone pair electrons occupy the sp hybrid orbital in amines, whereas three valence electrons lie in almost pure p orbitals and lone pair electrons occupy the remaining s orbital in bismuthines. 

Sulphur exists in several allotropic forms, and it has been found that the basic constituent of them all is a molecule of eight sulphur atoms Sg. The molecule has a ring structure and in it the sulphur atoms are considered to use sp3 hybridised orbitals (from the 3 and 3p orbitals). There is overlap between adjacent sulphur atoms by the two partly filled sp3 hybrid orbitals, and the two fully occupied sp3 hybrid orbitals constitute lone pairs. These... 

More probable representation of the water molecule. The bonding arises from overlap of oxygen sp3 hybrid orbitals with hydrogen Is orbitals. The lone pair on the oxygen is line shaded. The orbitals are displaced tetra-hedrally.. 

In such compounds as C1F3, the chlorine atom appears to use sp3d hybrid orbitals, two of the orbitals containing lone pairs of electrons, the other three, being partly filled, will be used for bonding with three fluorine partly filled p orbitals (one from each atom). 

To account for other molecular shapes within a given electron-group arrangement, we postulate that one or more of the hybrid orbitals contains lone pairs. In ozone (O3), for example, the central O is sp hybridized and a lone pair fills one of its three sp orbitals, so ozone has a bent molecular shape. 

The O atom is also sp hybridized and has an unhybridized p orbital that can form a TT bond. Two of the O atom s sp orbitals hold lone pairs, and the third forms a ct bond with the third sp orbital of the middle C atom. The unhybridized, half-filled p orbitals of C and O form a tt bond. The a and it bonds constitute the C=0 bond ... 

All have two double bond.s plus one lone pair in a p orbital = h it electrons, so all are aromatic. All have i-p -hybridized lone pairs on nitrogen, not tied up in the aromatic tt system, and therefore available to act in a Lewis-base manner. Pyrrole lacks an. sp -hybridized lone pair therefore all the compounds above arc stronger bases than pyrrole. 

HOMO = sulfur hybrid orbital containing lone pair... 

A result of the orbital mixing process in CO is a nicely hybridized lone pair orbital at carbon. As we have already pointed out, the rr orbitals of this molecule contain more carbon character. These two results mean that the carbon end of this unit can act (6.7) as a a donor and a tt acceptor, a feature of tliis molecule that will be very important in connection with its interaction with transition metals. 

Ollier than 90°, makes the actual 0 value smaller than 90°. With the bond orbital description, the gauche conformation of XChUOH is predicted by simply requiring one hybrid lone pair of oxygen to be antipcriplanar to a x- specifying various conformations of low-symmetry molecules containing OH groups, we will find it convenient to adopt a bond orbital description. 

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