Download R-c-H+H-oH:n-J-u oo o il o o o I o

Summary
of Reactions 415
S U M M A R YO F R I A C T I O ] T S
Here are the reactions of aldehydesand ketones presented in this chapter.
Aldehydes
1. Preparation of aldehydes:
OH
I
Oxidation,
R_C_H
I
5. Addition of waterto aldehvdes:
o
il
ooH
R-C-H
R-c-H+H-oH:n-J-u
H
I
OH
Primaryalcohol
Aldehyde
Aldehyde
hydrate
2. Oxidation of aldehydes:
6. Addition of alcohol to an aldehyde followed by a
second reactionwith an alcohol:
oo
oxidation,
n-A-oH
n-A-n
o
ll
R-C-H
Carborylic acid
OH
:
I
Ro-H
_
L
n-\_-n
II
3. Reaction of aldehydeswith Tollens' reagent:
o
il
RO-H
OR
Hemiacetal
OR
+
+ 2Ag+ + 2oH-
R-C-H
I
I
Silver
ions
R-C-H
OR
o
R-C-OH+
Carboxylic
acid
Acetal
2 A g ( s )+ H 2 O
Metallic
silver
Ketones
4. Reaction of aldehydes with Benedict's reagent:
1. Preparation
ofketones:
oH O
I -*
o
n-C-H
R- C
+
2Crt2*
+ 2OH
I
+
R-C-O-+
oxidatiorl,
n-c-n
H
Copper(II) ion
(blue solution)
o
I
+ H,O
Secondary
alcohol
2Cu*
Copper(I) ion
(red precipitate
ofCuzO)
+H2O
Ketone
2. Addition of alcohol to a ketone followed by a second reaction with an alcohol:
o
ll
R-C-R
OH
no-H
=-
I
R-C-R
I
OR
RO-H>
I
R-C-R
I
OR
OR
Hemiketal
Ketal
+ H2O
416
13 Aldehvdesand Ketones
CHAPTER
g{gYT#RfuTS
Benedict'sreagent(13.5)
Carbonylgroup (13.1)
Dehydrogenation reaction
(13.3)
Acetal (13.6)
Aldehyde (13.1)
Alpha-hydroxy ketone
(13.5)
Fehling'sreagent (13.5)
Hemiacetal(13.6)
Hemiketal (13.6)
Hydrate (13.6)
Ketal (i3.6)
Ketone(13.1)
Tollens'reagent(13.5)
HHtrffi{H#HS
TheCarbonyl
Group(Sections
15.1,15.2)
l3.l l
hat is the carbonyl group? Explain why a carboncarbon double bond is nonpolar, but a carbon-oxygen
double bond is very polar.
f3.12 Aldehydes and ketones are carbonyl compounds.
Draw their generalformulas.
13.13 Name the following aldehydesand ketones.
(a) CHgCHO
tur -,,\ \TCHO
(
RedoxReactions
of OrganicCompounds
|
5.5}
{Section
13.17 Classiff each reaction as an oxidation or a reduction.
(a) ethene ------ ethyne
(b) decanol_-decanal
(c) cyclopentanone ----- cyclopentane
(d) 3-hexanol ------3-hexanone
f 3.f 8 Iustify each classification in Exercise13.17in terms
ofloss or gain of oxygen and/or hydrogen.
ill
\/
'''o[g
(c)
Preparationof Aldehydesand Ketones
(Section15.4)
CH"
I
CH3CHCH2CHO
13.19 Give the names and structures of the expected
oxidation products from
(a) l-propanol
(b)
OH
I
(e)
CH.
ttl
cH3cH2ccH2cH3
I
CHs
O
cH3cHCH2CCH2CH3
13.14 Name the following aldehydesand ketones.
(a)
(c)
o
,0, ,r\__o
cH3icHs
\_/
cH3cH2cHCH2CH3
cH2cHo
cH3cH2ccH2cH2cH3
(e)
CH.
(d) cyclohexanol
OH
13.20 Write the structure of the product of the oxidation
of eachcompound. Name eachproduct.
(d)
o
(c)
CI
cH3cHCH2CHCH2CHO
13.15 Propane(CH.CH2CHT)and acetaldehyde
(CH3CHO)have the same molar mass,but propane
boils at -42"C, whereasacetaldehydeboils at 20'C.
\Mhy are the boiling points so different?
f3.f6 Explain why aldehydesand ketones cannot form
intermolecular hydrogen bonds but can form hydrogen
bonds with water molecules.
(a)
(b) cH3(cHr6cH2oH
f".
cH3cHoH
(c) 2-methyl-1-butanol
(d) acetaldehyde
13.21 Write the name and structure for the aldehyde or
ketone that must be reduced to make each of the following alcohols.
(a) methanol
(b)
oH
I
cHscHCH3
(c)
?".
CH3CHCH2OH
Exercises 417
13.22 Write the name and structure for the aldehyde or
ketone that must be reduced to make each of the following alcohols.
(a) 2-methylcyclopentanol
(b) cH3cH2oH
(c) 2-hexanol
Detectionof Aldehydes(Section15.5)
13.23 \Arhichof the oxidation products in Exercise13.20
will give a positive Benedict'stest?
13.24 \t\trich of the carbonyl compounds that were reduced in Exercise13.22will give a positive Tollens' test?
AdditionalExercises
13.29 Give the product of each of the following reactions.
If there is none, write "no reaction."
(a)
OH
cH3cHCH(Cnr),
#?F
(b)
gH.
I
KzCrzOz
CH3CHZCHCH2OH H2S04 ,
(c)
OH
I
CH.CH,CCH,CH"
--t
AdditionReactions
{Sectionll.6)
CHs
13.25 Write the structure for the hemiacetal that is
formed when ethanol is added to propanal.
13.26 Write the structure for the acetal that is formed
when an excessof methanol is added to ethanal.
13.27 Which of the following structures are acetals,
hemiacetals,or neither?
(a)
,,
f".
,0,
OH
(c)
?"".
(
\__J
lo-incHrcn.
(e)
il
cH.cHicH,
_ _l
__
ffl
"'
u,.-
j --{
reagent
Ni + Heat
+ H, ffi
CH3CHO
(h)
o
ll
CH3CCH3+ CH3CH2OH+
-''-''1*-l
13.30 Give the major organic product of each of the
following reactions.
(a)
O
tl
, .-,^\
\
t-
(b)
?r"'
c-ocH3
Benedict's,
"
CHs
13.28. lVhich of the following are acetals,hemiacetals,or
neither?
(a)
OCH" -
cH3cHoH
O
G) cH3cHo + cH3oH -
OCH2CH3
(d)
rollens',
reagent
ctt.cHcH,cHo
--I
CH.
t"
OH
cH3cH2cHocH2cH3
(d)
OH
cH3-c-cH3
I
cH3-c-ocH3
|
|
It l
\_,--
l+2cH.oH-l-
H*
o
ll
cH3cH2cH2cH
#F
o
(c)
.
CH
H
(c)
?cH'
l
cH3cH2-cHoH
(d)
OH
I
CH3CHOCH2CH3
Benedict's
+
rea8ent
o
cH3cHC-H
I
(d)
K2Cr2Or.
H2S04
OH
Benedict's
reagent
418
CHAPTER
15 Aldehvdes
and Ketones
13.31 Identify the following structures as acetals,hemiacetals,ketals, or hemiketals.
(a)
(b) cHs-cH-oH
f",
I
ocH3
cH3-c-ocH3
1,.
ocH2cH3
(c)
H,C/
-ll
H2C\
(d)
Hz
C_
\O
.-,-'
H,
v.;
cHzQ
I
I
H2C-C\
,/CH-OCH3
C
H2
l,/
on
13.35 You are given a compound and told that it is either
CH3CH2COCH3
or CH.CH2CH2CHO.
What laboratory
test(s)would you perform to identit/ the compound?
13.36 Draw structural formulas for the following.
(a) 3-hexanone
(b) buty'raldehyde
(c) propanal
(d) diisobutyl ketone
(e) methanal
(f) methyl phenyl ketone
13.37 Name the following structures. (lVhere appropriate, give both the common name and the IUPACname.)
(a) HCHO
(b) CH3CCH3
CHt
(e) CHgCHz-CH-OCH3
ocH2cH3 \uu
!'
(c) cH3cH2cH2cHo
(fl
U!
"r,
/,ocH3
f,
H,C
-ll
O
H,C
-\,/
CH,
V
o
C
c-cH3
H2
13.32 Name the following compounds bythe IUPAC
system.
(a) CH3CH2CH2CHO (b) CH3CH2CCH3
o
(c) CICHzCHzCHO
(d) CH3CHBTCCH2CH3
o
(e) FCHzgHCH2ccH2cH2cH3
tilll
(d)
(fl cH3ccH2cBr3
oHoo
13.33 The boiling points of ethyl methyl ether and
propanone are 11 and 56'C, respectively,but their
molecular weights are very similar. Explain.
13.34 \A/hichpairs of the following molecules form hydrogen bonds?Draw structures to show the hydrogen
bond, if formed.
(a) acetone and diethyl ether
(b) acetoneand acetone
(c) acetone and water
(d) acetone and acetaldehyde
(e) acetaldehydeand water
G) cH.cHr-c-cH2cH3
o
13.38 Write equations for the following reactions. Identify the classof compound(s) formed.
(a) the oxidation of 2-propanol
(b) the addition of water to acetone
(c) the reduction of formaldehyde
(d) the stepwiseaddition of two moles of ethanol to
one mole of acetaldehyde
13.39 Which member of eachof thesepairs of compounds would releasemore energy upon complete
oxidation?
(a) butanol, butanal
(b) ethene, ethane
(c) carbon dioxide, formaldehyde
(d) isopropyl alcohol, acetone
Self-Test(Review)
419
sffirF-?ffigT
{RHVEH$f}
True/False
l. A dehydrogenation reaction is a reduction reaction.
2. Hydrogen bonding accounts for the relatively high
boiling point of acetaldehyde.
3. The reaction of equal moles of an alcohol and an
aldehyde gives an acetal.
4. Oxidation of a tertiary alcohol gives a ketone.
5. You would expect propanal to have a higher boiling
point than propanol.
6. Propanal should have higher water solubility than
hexanal.
7. One mole of methanolwould releasemore energy
upon complete oxidation than one mole of methane.
B. Both aldehydesand ketones have a carbonyl group.
9. All aldehydesand ketones give a positive Tollens' test.
10. Fourpairs ofelectrons are sharedinthe carbonyl
bond formed between an oxygen and a carbon atom.
MultipleChoice
ll. Which of the following statements about the carbonoxygen double bond ofthe carbonyl groupis false?
(a) The bond is polar.
(b) The carbon has a partial negative charge.
(c) The bonding electrons are unequally shared
between the carbon and oxygen.
(d) The oxygenhas two unshared pairs of electrons.
12. Acetaldehydewould be likely to form hydrogen
bonds with
(a) formaldehvde.
(b) octane.
(c) water.
(d) acetone.
13. On the basis of your knowledge of intermolecular
forces,which of the followingwouldyou expect to
have the highest boiling point?
(a) prop-anal
(b) propane
(c) acetone
(d) 1-propanol
14. \tVhichof the following compounds contains a diether linkage?
(a) a hemiacetal
(b) chloral hydrate
(c) aketal
(d) camphor
15. \tVhichof the following substancesis used as a preservative of biological specimens?
(a) paraldehyde
(b) formalin
(c) methyl ethyl ketone
(d) cinnamaldehyde
16. \Mhich of the following substancescan undergo an
addition reaction with methanol?
(a) propane
(b) methyl ethyl ether
(c) propanol
(d) propanal
17. A structural isomer of 2-butanone is
(a) diethyl ether.
(b) tert-butyl alcohol.
(c) diethylketone.
(d) butanal.
lB. Which of the following compounds would releasethe
most energy upon oxidation to carbon dioxide?
(a) ethanol
(b) acetic acid, CH3COOH
(c) ethane
(d) acetaldehyde
19. The oxidation of 2-methyl-2-butanol with KrCr2OT
and H2SOawould give
(a) 2.methyl-2-butanone.
(b) isopropyl alcohol and ethane.
(c) 2-methyl-2-butanal.
(d) none ofthe above.
20. In a positive Tollens' test,
(a) silver ions are oxidized to silver atoms.
(b) the aldehyde is an oxidizing agent.
(c) a silver mirror is formed.
(d) more than one are correct.
21. In the reaction of substanceAwith substance4
substanceA loses oxygen.\dhich of the following is
true?
(a) SubstanceBis an oxidizing agent.
(b) SubstanceA is reduced.
(c) SubstanceBisreduced.
(d) SubstanceAis a reducing agent.