Chemistry 242 Exam #3 Summer 2010
The third exam is scheduled for Monday, July 26, covering material in Chapter 10, 17, and 18 of the text. The test will focus on chemistry of alkyl halides and alcohols, and organic synthesis.
The following textbook sections will be covered on the exam:
10.1 to 10.7, 10.10 18.1 – 18.3
17.1 to 17.9 17.12 (NMR only) (skip sections 17.10, 17.11)
It is particularly important to study and do the problems for the following sections:
10.4, 10.6, 10.7 17.4 17.5 17.6 17.7 18.3
Questions that may appear on the exam:
What is the name for this alkyl halide / alcohol / ether? Is an alcohol 1°, 2°, or 3°?
What are the products of free radical halogenation of an alkane (ex: Cl2/uv light)?
Give the chain mechanism for free radical halogenation.
What is the selectivity for brominations vs. fluorinations?
Why are allylic radicals more stable than other types? Draw resonance for all allylic radicals.
What is the definition of oxidation?
Which compound is at a higher oxidation state? Is this reaction an oxidation, reduction, or neither?
Describe hydrogen bonding in alcohols, and compare alcohol polarity to ether polarity.
What are the acid/base properties of alcohols? Rank the alcohols in order of acidity.
How are Grignard reagents prepared? Describe their bond polarity.
Use the Williamson ether synthesis (SN2 reaction of RO-) to prepare an unsymmetrical ether.
Given the NMR and molecular formula, what is the structure of this alcohol, ether, or alkyl halide?
Preparation of Alkyl Halides:
Free-radical halogenation of an alkane with uv light.
SOCl2 and PBr3 (R-OH to R-X for 1°/2° alcohols)
HCl / HBr (R-OH to R-X for 3° and allylic alcohols)
Allylic bromination reactions using NBS (N-bromosuccinimide)
Preparation of Alcohols:
Hydration of alkenes: acid-catalyzed addition of water (Markov.) or BH3/ox (Anti-Markov.)
SN2 reaction of an unhindered alkyl halide R-X with OH- to form the alcohol R-OH
Reduction of carbonyl compounds: NaBH4 (ald/ketones), LiAlH4 (ald/ketones/esters)
**Addition of Grignards (RMgX) or R-Li to aldehydes and ketones: mechanism, limitations.
Reactions of alcohols:
Deprotonation with strong base (NH2-, K metal) to form the alkoxide: RO–
Oxidation to carbonyl compounds: PCC or CrO3 (know when to use which reagent)
Conversion to R-X: dry HBr/HCl, PBr3, SOCl2 (know when to use which reagent)
Elimination to alkenes - POCl3 (all alcohols) or H2SO4 (for 3° alcohols)
Protecting –OH groups: Me3Si-Cl/Et3N (TMS chloride/weak base) puts on TMS ether;
aqueous acid removes protecting group
Williamson ether synthesis – know how to synthesize an ether
Remember: “The nucleophile attacks the carbonyl carbon!”
Chem 242 Review Problems - Exam 3
- Draw out the expected product.
- Show how each starting materials could be transformed into the product shown. Give reagents and draw the product for each step.
- Give two ways to prepare these two alcohols from a carbonyl compound and a Grignard reagent.
- Starting with methane, propose a synthesis of ethanol