Chem R340 Exam 2 Study Topics
Chapter 4
1. Nomenclature of alkenes
a. naming alkenes using systematic nomenclature
b. structure of alkenes and geometric isomerism
i. sp2 hybridized carbons, planar bond, no rotation of double bond
ii. cis/trans isomers of alkenes
iii. naming alkenes using the E,Z system
2. Stability of alkenes
a. the more alkyl-substitutuents there are on an alkene the more stable it is
b. trans alkenes have less steric strain than similar cis alkenes
3. Reactions of alkenes and curved arrow mechanisms
a. electrophiles, "electron loving", can accept a pair of electrons
b. nucleophiles, "nucleus loving", have a pair of electrons to share with a
nucleus
c. curved arrows show the movement of electrons
i. the electrons move from the base of the arrow to where it is
pointing
ii. double headed arrows show the movement of 2 electrons
iii. single headed arrows show the movement of 1 electron
iv. curved arrows show how bonds break and form during a reaction
mechanism
d. electrophilic addition of hydrogen halides (like HBr) to alkenes
i. mechanism
ii. reaction coordinate diagram, reactants, transition states,
intermediates, and products
Chapter 5
1. Addition reactions of alkenes
a. carbocation stabilities
i. (most stable) tertiary > secondary > primary > methyl cation (least
stable)
b. Markovnikov rule
i. the rich get richer (hydrogen rich carbons get more hydrogen)
c. types of addition reactions and mechanisms
i. addition of hydrogen halides to alkenes
ii. addition of water to alkenes
iii. addition of alcohols to alkenes
2. Alkynes
a. systematic nomenclature of alkynes
b. structure: sp hybridized, linear
c. addition of hydrogen halides to alkynes
3. Physical properties of alkenes and alkynes
4. Addition of hydrogen to alkenes and alkynes
5. Synthetic polymers
a. monomers and polymers produced from alkenes
i. alkene monomers
ii. polymers are alkane chains made from alkene monomers
b. polymerization reactions
i. cationic polymerization
ii. radical polymerization
6. Radicals in biological systems
a. radical inhibitors (vitamin C, vitamin E...)
Chapter 6
1. Types of isomers
a. constitutional isomers
b. stereoisomers
i. cis/trans and E/Z isomers
ii. isomers that contain asymmetric centers
1. enantiomers
2. diastereomers
2. Chiral objects have nonsuperimposable mirror images, achiral objects have
superimposable mirror images
3. Chiral molecules
a. asymmetric centers: atoms bound to 4 different groups
b. enantiomers, molecules with nonsuperimposable mirror images
i. drawing enantiomers with perspective formulas
ii. naming enantiomers using the R,S system
c. physical properties of enantiomers
i. enantiomers have the same boiling points, melting points, and
same solubilities
ii. enantiomers differ in optical activity: ability to rotate plane polarized
light
1. racemic mixtures do not rotate plane polarized light
d. molecules with more than one asymmetric center
i. 2n isomers for a molecule with n asymmetric centers
ii. enantiomers have completely reversed configurations
iii. diastereomers are stereoisomers that are not enantiomers
e. enantiomers have no difference in their reactivity with achiral molecules
f. enantiomers show differences when reacting or interacting with other
chiral molecules
i. enzymes and receptors produced in biological systems are chiral
and so show different interactions and reactivities with enatiomers
1. the drug thalidomide is an example where one enantiomer
behaves very differently than the other in biological systems
Chapter 7
1. Molecules with delocalized electrons
a. structure of carbonate (CO32-) and benzene
b. resonance contributors and resonance hybrids
c. drawing resonance contributors
d. stability of resonance contributors
e. stability of molecules with delocalized electrons
i. increased stabilization of allylic and benzylic carbocations
2. Effects of delocalized electrons on reactions, acidity, and UV/vis absorbance
a. stabilization of carbocations by delocalized electrons can effect the
product of addition reactions
b. isolated dienes and conjugated dienes react differently
i. conjugated dienes can have 1,2 and 1,4 addition products due to
resonance
c. delocalized electrons can affect pKa
i. acidity of acetic acid vs. ethanol
ii. phenol vs. cyclohexanol
iii. aniline vs. cyclohexylamine
d. molecules with conjugated double bonds absorb light at different
wavelengths compared to molecules without conjugated double bonds
i. the more conjugated double bonds there are the longer the
wavelength of light that is absorbed
ii. molecules with very many conjugated double bonds can absorb
light in the visible spectra and are colored (β-carotene, orange)
Chapter 8
1. Aromaticity
a. criteria for aromaticity
i. aromatic molecules must have an uninterrupted cloud of π
electrons above and below the plane of the molecule
1. must be cyclic
2. every atom of the ring must have a p orbital
3. each p orbital must overlap with p orbitals on either side of it
ii. the π electron cloud must have an odd number of pairs of electrons
b. aromatic compounds are planar
c. heterocyclic compounds can be aromatic