how to determine hybridization, MO vs. VB theory

Single Bond vs. Double Bonds:

• valence bond theory describes how double bonds “lack” molecule from spinning along a single bond

  • more rigid - gives definite shape-affects properties

• no spinning with graphite or diamound

• 11-cis-retinal(when light hits eye)

  all-trans-retinal

3 types of fat;

• saturated fatty acid(no double bonds) > all carbons are bond with Sp3 hybrids all through (Solidds)

• unsaturated-trans(H atoms opposite)>at least one carbon bond that is sp2 hybridize (Solidds)

• unsaturated - cis (H atoms same size)>Sp2 hybridize mp down

  • bent configuration

• where the double bond happens where the hydrogens are dilates the behaviors of this molecule

• LDF=surface area

Sigma/Pi bouds in following structures:

• first bond=sigma bond

• single bond= sigma sign

• every extra line = pi bond'

• 47 sigma sign

• 2 pi sign

• 47/2

what is the hybridization of the carbons with the arrow?

• regions of e-

• where are the e-?

• 3 regions for either C

• S ppp ddddd

  • S pp

  • Sp²

• S ppp ddddd

  • S ppp

  • Sp³

• Sp2

what does MO theory tell us that lewis /valence bond theory doesnt?

• take O2 for instance - 2 unpaired electrons in anti bonding pi star orbital

  • this means that O2 is a diradical

  • this also means that O2 is a paramagnetic

  • this info doesn’t rlly come out in VB theory (all paired e-)

• VB theory limited in terms of how it allows to understand how molecules form within their properties unpaired e- = radical

heteronuclear molecules: (not that important)different atoms can combine to form molecules

→ these atons have different atonic orbital energies - based on electronegatity

→ O is lower in enery than N

→ lower energy Als contribute more to the bonding MO → higher exegy 101 → more antibonding MOS

Non bonding electrons:

• if the energy difference bw atoms is so great, the result is that atom will not contribute its electrons to the molecule

  • non bonding electrons

  • HF-fluroine is so electronegative that it doesnt contribute some of its electrons to the bonds

Ozone O3:

• MO theory more encompassing VS. VB theory

  • eliminates octet rule, the “2 electrons for a bond” rule

  • explains why certain molecules are stable/unstable

  • explains reactivity

  • explains resonance

Bonding theories recap:

• MO theory and VB theory help us to understand how molecules can form

• based on understand electrons in the atom

  • VB theory: orbitals overlap+electrons are located bw the atoms

    • orbitals can hybridize and this explains the shape of molecules and molecular properties

  • MO theory: waves can overlap in lower engird (stabilizing) ways or higher engergy (destabilizing) ways

    • if more electrons fill the stabilizing molecular orbitals, bond can form

• important to realize that these are just models- ways to think abt + explain molecular behavior