Chapter 18 Amines and Neurotransmitters - …websites.rcc.edu/grey/files/2014/08/Chapter-18.pdfChapter 18 Amines and Neurotransmitters ... 18.1 To determine whether an amine is 1o,
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Chapter 18–1
Chapter 18 Amines and Neurotransmitters Solutions to In-Chapter Problems 18.1 To determine whether an amine is 1o, 2o, or 3o, count the number of carbons bonded to the nitrogen
atom as in Example 18.1. A 1o amine has one C–N bond, and so forth.
NC6H5
CCH3CH2O
O
CH3a. b.H2N(CH2)3NH(CH2)4NH(CH2)3NH2
1o 2o 2o 1o3o
18.2 Label the amine and hydroxyl group in scopolamine, a drug used to treat motion sickness, as 1o, 2o,
or 3o as in Example 18.1.
NCH3
O C CHO
CH2OH
O
scopolamine
3° amine1° hydroxyl group
18.3 Methamphetamine is a 2° amine. Give the molecular shape around each atom by counting groups.
18.51 The hydrogen bond is drawn as a dashed line.
NCH2CH3
HCH2CH3
NCH3CH2
CH3CH2H
18.52 The hydrogen bond is drawn as a dashed line.
NCH3CH2
CH3CH2H
OH
H
18.53 Primary amines can hydrogen bond to each other, whereas 3o amines cannot. Therefore, 1o
amines have higher boiling points than 3o amines of similar size. Since all amines contain nitrogen atoms, any amine can hydrogen bond to water. Therefore, 1o and 3o amines have similar solubility properties.
18.54 CH3(CH2)5NH3
+Cl is more water soluble than CH3(CH2)5NH2 because the ammonium salt is an ionic solid and therefore soluble in water. CH3(CH2)5NH2 contains six carbons and is therefore not water soluble.
18.55 Draw the reaction of each amine with water by transferring a proton from H2O to the amine.
a. CH3CH2NH2 + H2O (CH3CH2NH3)+
+ OH–
+
b. (CH3CH2)2NH + H2O (CH3CH2)2NH2 + OH–
+
c. (CH3CH2)3N + H2O (CH3CH2)3NH + OH–
18.56 Draw the ammonium salt that is formed when each amine is treated with HCl.
18.61 The heterocycle in both coniine and morphine is piperidine (labeled in bold).
O
HO
NCH3HO
morphine
NH
CH2CH2CH3
coniine
18.62 The pyrrolidine N is trigonal pyramidal because it is surrounded by four groups, three of which
are bonds and one of which is a lone pair of electrons. The pyridine N has only three groups around it, two of which are bonds and one of which is a lone pair. The pyridine N doesn’t have enough groups around it to be trigonal pyramidal.
N NCH3
trigonal pyramidaltrigonal planar 18.63 Caffeine is a mild stimulant, imparting a feeling of alertness after consumption. It also increases
heart rate, dilates airways, and stimulates the secretion of stomach acid. These effects are observed because caffeine increases glucose production, making an individual feel energetic.
18.64 Caffeine intake should be limited in pregnant and nursing mothers because excessive
consumption increases the risk of miscarriage and caffeine can pass into breast milk, possibly affecting the health of a newborn baby.
18.65 An alkaloid solution is slightly basic since its amine pulls off a proton from water, forming OH–
and an ammonium ion. 18.66 a. Morphine is found in poppies and is used as a pain reliever for people suffering from severe
chronic pain. b. Quinine is found in the bark of the cinchona tree and is used to treat malaria. c. Atropine is found in the nightshade plant and is used to increase heart rate.
18.67 Dopamine affects brain processes that control movement, emotions, and pleasure. Normal dopamine levels give an individual a pleasurable, satisfied feeling. Increased levels result in an intense “high.” Drugs such as heroin, cocaine, and alcohol increase dopamine levels. When there is too little dopamine in the brain, an individual loses control of fine motor skills and Parkinson’s disease results.
18.68 Patients with Parkinson’s disease cannot be treated by giving them dopamine, even though the
disease results from low dopamine levels, because dopamine does not cross the blood–brain barrier.
18.69 Serotonin plays an important role in mood, sleep, perception, and temperature regulation. We get
sleepy after eating a turkey dinner on Thanksgiving because the unusually high level of tryptophan in turkey is converted to serotonin. A deficiency of serotonin causes depression.
18.70 Two examples of SSRIs are fluoxetine (Prozac) and sertraline (Zoloft). They combat depression
by inhibiting the reuptake of serotonin by the presynaptic neuron. 18.71 Dopamine [part (a)] and norepinephrine [part (b)] are derived from tyrosine, serotonin [part (c)] is
derived from tryptophan, and histamine [part (d)] is derived from histidine. 18.72 A neurotransmitter is a chemical messenger that transmits nerve impulses from one nerve cell
(neuron) to another cell. A hormone is a compound produced by an endocrine gland, which then travels through the bloodstream to a target tissue or organ.
18.73 The atoms of 2-phenylethylamine are labeled in bold in the compounds below.
CH2CH2CH2NH2a. b. c.C
CH3
CH3
CH2N(CH3)2 CH2HN
not a derivative of2-phenylethylamine
18.74 The atoms of 2-phenylethylamine are labeled in bold in the compounds below.
a. b. c.CCH3
CH3
C CH2CH2
not a derivative of2-phenylethylamine
CH3
NHCH3
CH3 CH2NH N
18.75 The atoms of 2-phenylethylamine are labeled in bold.
18.76 The atoms of 2-phenylethylamine are labeled in bold.
CHCH2NHC(CH3)3HO
HOCH2
OH
18.77 Chlorpheniramine is an example of an antihistamine. Antihistamines bind to the H1 histamine
receptor, but they evoke a different response than histamine. An antihistamine like chlorpheniramine or diphenhydramine, for example, inhibits vasodilation, so it is used to treat the symptoms of the common cold and environmental allergies.
18.78 Cimetidine is an anti-ulcer drug. It binds to the H2 histamine, thus reducing acid secretions in the
stomach. 18.79 Answer each question about benzphetamine.
18.83 Work backwards to draw the structure of the amine and carboxylic acid that are used to form Chlortrimeton, an ammonium salt.
CHCH2CH2N(CH3)2
N
ClH
C CH
HOOC COO–
H
+
chlorpheniramine maleateChlortrimeton
CHCH2CH2N(CH3)2
N
ClC C
H
HOOC COOH
H
18.84 Draw the structure of the dextromethorphan hydrobromide.
CH3O
NHCH3
+ Br–
18.85 A vasodilator dilates blood vessels and a bronchodilator dilates airways in the lungs. Histamine is
a vasodilator and albuterol is a bronchodilator. 18.86 Antihistamines that cause drowsiness are able to cross the blood–brain barrier and bind to H1
receptors in the central nervous system. Antihistamines that do not cause drowsiness also bind to H1 receptors, but they are unable to cross the blood–brain barrier and bind to the H1 receptors in the central nervous system.