Download Exam 3 Review

Chemistry 242
Exam #3
Summer 2009
The third exam will be on Wed, July 29, covering material in Chapter 17 – 19 of the text. The test will
focus on chemistry of alcohols, ketones, aldehydes, and organic synthesis.
The following textbook sections will be covered on the exam:
17.1 to 17.9
17.12 (NMR of alcohols only)
(skip sections 17.10, 17.11)
18.1, 18.2, 18.3
19.1 to 19.11 and 19.16 skip enamines in 19.9
It is particularly important to study and do the problems for the following sections:
17.4 17.5 17.6 17.7
18.3
19.4 19.8 19.11
Questions that may appear on the exam:
What is the name for this alcohol / ether / aldehyde / ketone? Is an alcohol 1°, 2°, or 3°?
Describe hydrogen bonding in alcohols, and compare alcohol polarity to ether polarity.
What are the acid/base properties of alcohols? Rank these compounds in order of acidity.
How are Grignard reagents prepared? Describe their bond polarity. How do organolithiums react?
Use the Williamson ether synthesis (SN2 reaction of RO–) to prepare an unsymmetrical ether.
Why are aldehydes more reactive than ketones?
Classify the following compounds as either alcohols, diols, ethers, hemi-acetals, or acetals.
What is the mechanism of acid catalyzed acetal formation? (section 19.11)
Given NMR and molecular formula, what is the structure of this alcohol, aldehyde, or ketone?
Preparation of alcohols:
Hydration of alkenes: acid-catalyzed addition of water (Markov.) or BH3/ox (Anti-Markov.)
Reduction of carbonyl compounds: NaBH4 (ald/ketones), LiAlH4 (ald/ketones/esters)
SN2 reaction of an unhindered alkyl halide R-X with OH- to form the alcohol R-OH
**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 each reagent)
Conversion to R-X: dry HBr/HCl, PBr3, SOCl2 (know when to use each reagent)
Elimination to alkenes - POCl3 (for 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
Carbonyl Reactions:
Prep of aldehydes/ketones:
alcohol oxidation (PCC/CrO3) (also ozonolysis)
Rxn of aldehydes / ketones: reduction, Grignard reaction, acetal formation, hydration
imine formation, Wolff-Kishner reaction, cyanohydrin formation
Other Reactions: Williamson ether synthesis
Synthesis Problems: starting with an alkane (or other specified material), make the compound shown.
alkane + X2 / hv → haloalkane
RCH2Br + OH- → RCH2OH
Useful
R-Br + Mg → R-Mg-Br
RCH2OH + PBr3 → RCH2Br
Synthesis
RCH2OH + PCC → aldehyde
R2C=CR2 + H2 / cat. → alkane
Reactions
Wolff-Kishner:
Remember:
O
H2N-NH2
H
H
“The nucleophile attacks the carbonyl carbon!”
Exam 3
Review Problems
1. Show how each starting materials could be transformed into the product shown. Give reagents and
draw the product for each step.
O
OH
OH
OH
OH
OH
and
2. Show how ethanol can be made from methane:
CH4
→
→
CH3CH2OH
CH3CH3 → → CH3CH2CH2CH3
3. Show how butane can be made from ethane:
4. Show how ethylamine can be made from methane:
→
CH4
→
CH3CH2NH2
5. Give two different ways to prepare each alcohol from a carbonyl compound and a Grignard reagent.
OH
OH
Br
6. Starting with ethane, propose a synthesis of 1-butanol.
7. Starting with ethane, prepare:
H2N
OH
O
8. Using the Williamson ether synthesis, prepare the ether
shown from any starting materials.
9. Give products (after aqueous workup) for the four reactions below.
OH
OH
Ph
+ PBr3
Ph
+
CrO3
acetone
O
O
CH3CH2-Li
+
acetone
Et2O
H
+ 2 CH3OH
THF