Download Problem Set Chapter 8: Introduction to Alkyl Halides, Alcohols

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Problem Set Chapter 8: Introduction to Alkyl Halides, Alcohols, Ethers, Thiols, and
Sulfides
Substitutive Nomenclature
The principal group and the principal chain are the key concepts defined and used in the construction of a
substitutive name according to the general rules for substitutive nomenclature of organic compounds, which
follow.
O
O
O
O
Priority as principal group: (carboxylic acid) >
(anhydride) >
C OH
C O C
C O R
O
O
O
(ester) > C X (acid halide) >
(amide) > C N
(nitrile) > C H (aldehyde) >
C
NR
O
2
(ketone) >
OH (alcohol, phenol) >
SH (thiol) >
NR2 (amine)
C
1. Identify the principal group. When a structure has several candidates for the principal group, the group
chosen is the one given the highest priority by the IUPAC.
2.
Identify the principal carbon chain. The principal chain is the carbon chain on which the name is based.
The principal chain is identified by applying the following criteria in order until a decision can be made:
a. the chain with the greatest number of principal groups;
b. the chain with the greatest number of double and triple bonds;
c. the chain of greatest length;
d. the chain with the greatest number of other substituents.These criteria cover most of the cases you’ll
encounter.
3. Number the carbons of the principal chain consecutively from one end.. In numbering the principal chain,
apply the following criteria in order until there is no ambiguity:
a. the lowest numbers for the principal
b. the lowest numbers for multiple bonds, with double bonds having priority over triple bonds in case
of ambiguity;
c. the lowest numbers for other substituents;
d. the lowest number for the substituent cited first in the name.
4. Begin construction of the name with the name of the hydrocarbon corresponding to the principal chain.
a. cite the principal group by its suffix and number; its number is the last one cited in the name.
b. if there is no principal group, name the compound as a substituted hydrocarbon.
c. cite the names and numbers of the other substituents in alphabetical order at the beginning of name.
Hwk: 8.5, 7, 12-18, 26-28, 23-24 (misnumbered in textbook), 40-42, 44 46, 50-51, 54-59, 61.
8.5 Give the substitutive name for each of the following compounds.
(a) CH3 CH CH2 CH2 OH
(b)
H3C
(c)
CH3 CH2 CH2 CH2 OH
CH3
C
H
Br
C
CH CH2 Cl
OH
(d)
HO
Cl
H3C
StudyProbCh8-­‐1415.docx (e)
OH
H3C
CH
CH
CH
CH3
(f)
OH
CH3 CH2
CH2 CH2 CH3
1 (g)
CH3 CH2 CH2 CH CH2 SH
CH3
(h)
H3C
OH
C
CH3
SH
8.7 Give the substitutive name for each of the following compounds.
(a)
(CH3)3C O CH3
(b)
(c)
CH3 OCH2
(d)
C
H
CH3 CH2
O
CH2 CH2 OH
S
C
H
CH2 CH2 OH
8.12 The boiling points of the 1,2-dichloroethylene stereoisomers are 47.4 °C and 60.3 °C. Give the structure of
the stereoisomer with the higher boiling point. Explain.
8.13 Within each set, arrange the compounds in order of increasing boiling point.
(a) 4-ethylheptane, 2-bromopropane, 4-ethyloctane
(b) 1-butanol, 1-pentene, chloromethane
8.14 Label each of the following molecules as a hydrogen-bond acceptor, donor, or both. Indicate the hydrogen
that is donated or the atom that serves as the hydrogen-bond acceptor.
• •
(a)
H
••
(b)
Br ••
••
H
•O•
••
F ••
••
(c)
H3C
C
(f)
H3C
CH2 NH3
CH3
• •
•O•
(d)
H3C
C
••
NH CH3
(e)
••
OH
+
••
8.15 Classify each of the following substances according to their solvent properties (polar/nonpolar;
protic/aprotic; donor/nondonor).
(a) 2-methoxyethanol (ε = 17)
(b) 2,2,2-trifluoroethanol (ε = 26)
(c) 2-butanone (ε = 19)
(d) 2,2,4-trimethylpentane (ε = 2)
StudyProbCh8-­‐1415.docx 2 8.16 In which of the following solvents should hexane be least soluble: diethyl ether, methylene chloride
(CH2Cl2), ethanol, or 1-octanol? Explain.
8.17 (a) Into a separatory funnel is poured 200 mL of methylene chloride (density = 1.33 g/mL) and 55 mL of
water. This mixture forms two layers. One milliliter of methanol is added to the mixture, which is then
stoppered and shaken. Two layers are again formed. In which layer is the methanol likely to be dissolved?
Explain.
(b) The experiment is repeated, except that 1 mL of 1-nonanol is added instead of methanol. In which layer
is the alcohol dissolved? Explain.
8.18 A widely used undergraduate experiment is the recrystallization of acetanilide
from water. Acetanilide (see following structure) is moderately soluble in hot
water, but much less soluble in cold water. Identify one structural feature of the
acetanilide molecule that would be expected to contribute positively to its
solubility in water and one that would be expected to contribute negatively.
• •
• O•
••
NH C
CH3
8.26 In each of the following sets, arrange the compounds in order of increasing acidity (decreasing pKa).
Explain your choices.
(a) ClCH2CH2OH, Cl2CHCH2OH, Cl(CH2) 3OH
(b) ClCH2CH2SH, ClCH2CH2OH, CH3CH2OH
(c) CH3CH2CH2CH2OH, CH3OCH2CH2OH
8.27 Give an equation showing the preparation of each of the following organometallic compounds.
(a) (CH3)2CH-MgBr
(b) CH3-MgI
StudyProbCh8-­‐1415.docx 3 (c) Ph-Li
(d) [(CH3) 2CH-CH2] 3B
8.28 Complete each of the following equations.
(a)
Br
+
(b)
THF
Mg
hexane
(CH3)3C-Cl + Li
8.24 (a) Give the structures of two isomeric alkylmagnesium bromides that would react with water to give
propane.
(b) What compounds would be formed from the reactions of the reagents in (a) with D2O?
8.40 Identify the gas evolved in each of the following reactions.
(b) Na + D2O
(d)
CH3 CH2 CH2 MgBr + H2O
OH
(e)
Na H + H3C
CH CH3
8.41 Identify the correct compound(s) in each case. Explain your choice.
(a) A compound believed to be either diethyl ether or propyl alcohol is miscible in water.
(b) A compound believed to be either allyl methyl ether or propyl alcohol decolorizes a solution of Br2 in
CH2Cl2.
StudyProbCh8-­‐1415.docx 4 (d) A compound believed to be either cyclohexyl methyl ether or 2-methylcyclohexanol evolves a gas when
treated with NaH.
8.42 (a) One of the following compounds is an unusual example of a salt that is soluble in hydrocarbon solvents.
Which one is it? Explain your choice.
CH2 CH2 CH2 CH3
+
CH3(CH2)15 N
CH2 CH2 CH2 CH3
-
+
Br
NH4
CH2 CH2 CH2 CH3
A Cl
-
B (b) Which of the following would be present in greater amount in a hexane solution of the compound in
part (a): separately solvated ions, or ion pairs and higher aggregates? Explain your reasoning.
8.46 Normally, dibutyl ether is much more soluble in benzene than it is in water. Explain why this ether can be
extracted from benzene into water if the aqueous solution contains moderately concentrated nitric acid.
8.50 The effectiveness of barbiturates as sedatives has been found to be directly related to their solubility in, and
thus their ability to penetrate, the lipid bilayers of membranes. Which of the following two barbiturate m
derivatives should be the more potent sedative? Explain.
barbital StudyProbCh8-­‐1415.docx hexethal 5 8.54 Ethyl alcohol in the solvent CCl4 forms a hydrogen bonded complex with an equilibrium constant
Keq = 11.
2 C2H5OH
••
••
C2H5 O••
H
O
••
C2 H5
H
(a) What happens to the concentration of the complex as the concentration of ethanol is increased? Explain.
(c) What is the standard free-energy change for this reaction at 25 °C?
(e) The equilibrium constant for the analogous reaction of ethanethiol is 0.004. Which forms stronger
hydrogen bonds, thiols or alcohols?
8.55 (a) The bromination of 2-methylpropane (isobutane) in the presence of light could give two
monobromination products; give their structures.
(b) In fact, the products consist of more than 99% of one compound and less than 1% of the other. Write the
mechanism for the formation of each compound, and use what you know about the stabilities of free
radicals to predict which compound should be the major one formed.
8.56 When sec-butylbenzene undergoes free-radical bromination, one major product is formed, as shown in Fig.
P8.56. If the starting material is optically active, predict whether the substitution product should also be
optically active. (Hint: Consider the geometry of the free-radical intermediate; see Fig. 5.3 on p. 210.)
StudyProbCh8-­‐1415.docx 6 8.57 Three alkyl halides, each with the formula C7H15Br, have different boiling points. One of the compounds is
optically active. Following reaction with Mg in ether, then with water, each compound gives 2,4dimethylpentane. After the same reaction with D2O, a different product is obtained from each compound.
Suggest a structure for each of the three alkyl halides.
8.59 Offer an explanation for each of the following observations.
(a) Compound A exists mostly in a chair conformation with an equatorial ─OH group, but compound B
prefers a chair conformation with an axial ─OH group.
OH
OH
O
O
A B (b) The racemate of 2,2,5,5-tetramethyl-3,4-hexanediol exists with a strong intramolecular hydrogen bond,
but the meso stereoisomer has no intramolecular hydrogen bond.
StudyProbCh8-­‐1415.docx 7