Chemistry 241 Final Exam Fall 2009
The final exam for Chem 241 will be held at 3pm on Tuesday, Dec. 15, covering Chapters 1 - 11.
The following sections of the text will NOT be covered on the exam:
1.122.92.133.54.64.74.134.145.35.8 6.1 6.11 6.12 7.1 7.6 7.9 7.10 8.1 8.3 – 8.5 8.7 – 8.10
9.10 9.12 – 9.17 10.3 - 10.610.8–10.1011.12 11.1311.16
It is particularly important to study and do the problems for the following sections:
1.7 1.92.12.42.113.23.4
4.3 4.9 4.125.25.45.6
6.2 6.6 6.8 6.97.27.57.78.6
9.2 9.5 9.69.1110.711.411.511.611.11
Know names and structures for the following functional groups:
alkane alkenealkynealdehyde
alkyl halide (haloalkane) alcoholcarboxylic acidketone
Topics for the Final Exam
Naming Compounds:alkanes, cycloalkanes, alkenes, alkynes, alkyl halides. Know the names methane through decane, alkyl groups names, common names isopropyl and t-butyl
Organic Structures:
orbital hybridization: sp3 sp2 sp
electron pair geometry: tetrahedral trig planar linear (atoms + lone pairs on central atom)
molecular shape: linear, bent, trigonal planar, trigonal pyramidal, tetrahedral
(consider just atoms around the central atom)
Lewis structures and resonanceFormal charges
Drawing proper organic structures
Bonding and Reactivity
Polar covalent bonds and electronegativity
Lewis acid-Lewis Base interactions
Reactions of organic acids (carboxylic acids) and organic bases (amines)
Electron pushing using curved arrows to show the flow of electrons in a reaction
Potential energy diagrams, transition states, intermediates, energy of activation ΔG‡
Substitution and elimination reaction mechanisms (SN2, SN1, E2, E1) with leaving groups
Addition reaction mechanisms (Markovnikov/Ant-Mark.) with alkenes
Identify nucleophiles, electrophiles, leaving groups; acids and bases.
Alkane and Cycloalkane Conformations
Newman projections: eclipsed, staggered, anti, gauche, and relative energies
Chair cyclohexane: drawing axial and equatorial bonds, most stable chair conformation
Classify carbons and hydrogens: 1° (primary), 2°, 3°
Isomers and Stereochemistry
Identifying chiral molecules and other objects – use plane of symmetry test
Circle chiral centers in a molecule
Isomers – constitutional isomers, two types of stereoisomers: enantiomers and diastereomers
Define: isomer types, chiral, achiral, optically active, racemic, meso
Naming enantiomers – assign priority to each group and determine R or S designation
Number of possible stereoisomers – use the 2n rule
Alkenes
Degree of unsaturation for a molecular formulaHybridization; cis/trans and E/Z names
Alkene stable (more substituted means more stable)
Selectivity in alkene addition reactions: Markovnikov vs. Anti-Markov.syn vs. anti
Preparation of an alcohol from an alkene
Alkene Reactions
HCl or HBr + inert solvent (CH2Cl2, CCl4)Cl2 or Br2 + inert solvent (CH2Cl2, CCl4)
H2SO4/H2O (Markovnikov)Hg(OAc)2 /H2O; reduction (Markovnikov)
BH3; oxidation (Anti-Markov.)H2/catalyst (for catalytic hydrogenation)
OsO4; reduction (make diol)O3; reduction (alkene cleavage)
reaction mechanisms – carbocation intermediate, bromonium ion intermediate, syn vs. anti addn.
Alkynes
Naming alkynes (use –yne ending)Reduction of alkynes to alkanes (H2/cat)
Alkyl Halides
Naming and bonding in haloalkanes
Prep. of R-X from an alcohol:HCl/Et2O or HBr/Et2O to prepare the 3° alkyl halide (SN1)
SOCl2 or PBr3 to make 1° and 2° alkyl halides (SN2)
Substitution and Elimination
Reaction Mechanisms: SN2, SN1, E2, E1
Carbocation stability: 3° most stable, 1° least stable
Transition states, intermediates, and potential energy diagrams for SN2/SN1/E2/E1 reactions
Ranking compounds in order of nucleophilic strength; ranking reactivity of electrophiles (R-X)
Nucleophile:strength of a nucleophile increases when:
adding a negative chargeRO– stronger than ROH
moving left on the periodic tableNH2– stronger than OH–
moving down the periodic tablePH3 stronger than NH3
Base:strength of a base increases when:
adding a negative chargeRO– stronger than ROH
moving left on the periodic tableNH2– stronger than OH–
moving up the periodic tableNH3 stronger than PH3
Leaving Grp -good leaving groups are –OTos, –I, –Br, –Cl, and any neutral fragment (H2O)
poor leaving groups are –F, –OH, –NH2, –OR, –CH3
Key Factors for Reaction Mechanisms
SN2 Reactions – unhindered electrophile (1°, maybe 2° alkyl halide) and a good nucleophile
(no SN2 reaction at 3° carbons)
SN1 Reactions – stable carbocation (3°, allylic, or benzylic) and protic solvent (ROH or H2O)
Also, no strong nucleophile/base present!
E2 Reactions – a strong base (neg. charged C, N, O, P, S) is required for E2
you also must have an H on the carbon next door to the leaving group
E1 Reactions - stable carbocation (3° or allylic or benzylic) and protic solvent (ROH or H2O)
Also, a weak base (CO32- or R3N: ) will help promote E1 mechanism
Know what starting materials to use to synthesize a desired product.