1. Organic Chemistry - 246A Homework DUE Friday, 5 Sept
Problems in McMurry
1.24; 1.28; 1.31; 1.45; 1.46; 1.47
=> (1.48—1.52 BONUS Problems)

2. Hybridization of C, N & O sp3, sp2 & sp Bonding Structure & Bonding (Chapter 1, pp 1—28)
All of these atoms can be involved in single, double, and triple bonds
sp3 Orbitals make single bonds (s) bonding e—
sp2 Orbitals make double bonds (s + p) bonding e—
sp Orbitals make triple bonds (s + p + p) bonding e—

3. Ethylene H2C=CH2 sp2 orbitals are in a plane with120° angles
90
120
sp2 orbitals are in a plane with120° angles
The remaining p orbital is 90° perpendicular to the plane containing the sp2 orbitals
Two sp2 orbitals interact to form a double bond, one s-bond one p-bond

4. Dihedral Rotation of Ethane

5. Dihedral Rotation of Ethylene

6. p-p Overlap Required for p-Bond
No Overlap pZ pZ
No Longer
pZ Orbital

7. H2C=CH2 Structure
The C=C double bond is shorter (1.33 Å) than a single C—C bond (1.54 Å)
C=C is much stronger (611 kJ/mol) than a single C—C bond (376 kJ/mol)

8. Acetylene HCCH
Two sp hybrid orbitals from each carbon overlap to form one sp–sp s-bond
In addition, the pz orbitals from each carbon form a pz–pz  bond by sideways overlap and py orbitals overlap similarly

9. s + p + p Bonding in Acetylene
Sharing of 6 valence e— forms a triple bond (s + 2p)
The two sp orbitals at the ends form s-bonds with the terminal hydrogens

10. Acetylene Structure
The triple bond length in acetylene (1.20 Å) is far shorter than ethane (1.54 Å) or ethylene (1.33 Å)
The triple bond is far stronger (835 kJ/mol)

11. Hybridization of Nitrogen
In ammonia, NH3, the nitrogen atom has 5 outer-shell e— and it forms 3 covalent bonds with 3 hydrogen atoms to fill its valence e— octet
H–N–H bond angle in NH3 is 107.3°, close to the tetrahedral angle observed in methane CH4
One sp3 orbital is occupied by a lone pair of e—, and 3 sp3 orbitals have one electron each, forming bonds to the 3 H atoms
NH3, the N–H bond length is pm, and bond strength is 449 kJ/mol

12. The Nitrogen Lone Pair is Basic
Nitrogen-containing compounds derived from :NH3 are the most common organic bases
The lone pair on :NH3 can form a bond with H+ to form an ammonium ion +NH4
We can refer to this process as protonation of a lone pair, and such a lone pair is referred to as a protonated lone pair

13. sp2 and sp Hybridized Nitrogen
Carbon-nitrogen double bonds (C=N) are called imines
Sections and (pp 696—702) cover the some important reactions that produce and use imines
Carbon-nitrogen triple bonds are called nitriles (cyanides)
These important compounds are generally regarded as derivatives of carboxylic acids (Chapter 20)

14. Hybridization of Oxygen
The oxygen atom in H2O is sp3-hybridized
Oxygen has 6 valence-shell e— but forms only 2 bonds, leaving two lone pairs
The H–O–H bond angle in water is 104.5°— This is less than the tetrahedral angle due to e— e— repulsion between the two lone pairs
The O–H bond length is 95.8 pm, and the bond strength is 498 kJ/mol
The e— e— repulsion pushes
the two H’s closer together

15. sp2 and sp Hybridized Oxygen
Carbon-oxygen double bonds (C=O) are called carbonyls
Carbonyls are present in aldehydes, ketones, carboxylic acids, carboxylic esters, and amides (peptide bonds)
Understanding the carbonyl and its reactivity are among the most important concepts in Organic Chemistry
sp hybridized oxygen is extremely rare in Organic Chemistry
The only important example is carbon monoxide CO

16. Protonation of Oxygen
Oxygen lone pairs are not as basic as nitrogen lone pairs, but can be protonated by strong acids
Protonation of oxygen provides intermediates that are very important for catalysis