D) anomer
E) achiral isomer
8. Which of the following organic structures is a chiral compound?
A) CH3-CH2-CH2-OH
B) CH3-CH(Br)-CH3
C) CH3-CH(OH)-CH2-CH3
D) (CH3)2CH-OH
E) CH2(Cl)-CH2(Cl)
CHEM 1406 | Exam 4 Review Package Page 1 of 4
Organic Chemistry & Biochemistry Practice Exam
PRACTICE TEST
9. What is the correct IUPAC name for the following carboxylic acid?
CH3-CH(Cl)-CH2-CH2-COOH
A) 2-chloropentanoic acid
B) 4-chloropentanoic acid
C) 4-chlorobutanoic acid
D) 3-chlorovaleric acid
E) γ-chloropentanoic acid
10. Which of the following compounds is classified specifically as an aromatic carboxylic acid?
A) Phenol
B) Benzoic acid
C) Cyclohexanecarboxylic acid
D) Acetic acid
E) Aniline
11. An acidic amino acid (such as aspartate) has a unique side chain containing which functional group at physiological pH?
A) Ammonium group
B) Hydroxyl group
C) Thiol group
D) Carboxylate group
E) Amide group
12. When the amide N-methylbenzamide is hydrolyzed under basic conditions with NaOH, what are the product(s) obtained?
A) Benzoic acid and methylamine
B) Sodium benzoate and methylamine
C) Sodium benzoate and methylammonium chloride
D) Benzyl alcohol and methylamine
E) Benzene and methylamide
13. Which of the following organic compounds exhibits the highest solubility in water?
A) CH3-CH2-CH2-CH3
B) CH3-CH2-COO- Na+
C) CH3-CH2-CH2-O-CH3
D) CH3-CH2-CH2-CH2-OH
E) CH3-CH2-CH2-CO-NH-CH3
14. What type of non-covalent interaction would you expect between an aspartate side chain (-CH2-COO-) and a lysine side chain (-(CH2)4-NH3+) in a protein's tertiary structure?
A) Disulfide bonds
B) Hydrogen bonds
C) Salt bridges
D) Hydrophobic interactions
E) Peptide bonds
15. In the Haworth cyclic projection of D-glucose, if the hemiacetal hydroxyl group (-OH) on Carbon-1 is oriented pointing downward, this indicates the ________ isomer.
A) alpha (α)
B) beta (β)
C) delta (δ)
D) L-enantiomer
E) keto
16. The correct one-letter abbreviation for the aromatic amino acid tyrosine is ________.
A) T
B) Y
C) W
D) P
E) R
CHEM 1406 | Exam 4 Review Package Page 2 of 4
Organic Chemistry & Biochemistry Practice Exam
PRACTICE TEST
17. Structural isomers that are nonsuperimposable mirror images of each other are referred to specifically as ________.
A) Anomers
B) Diastereomers
C) Enantiomers
D) Epimers
E) Conformers
18. In the α-helix secondary structure of a protein, the localized coiled conformation of the polypeptide backbone is stabilized by ________.
A) disulfide linkages
B) hydrophobic exclusion
C) salt bridge linkages
D) backbone hydrogen bonding
E) peptide bond synthesis
19. A biological macromolecule containing a sequence of more than 50 amino acids linked by peptide bonds with definitive biological function is called a(n) ________.
A) Oligopeptide
B) Polypeptide
C) Protein
D) Nucleic acid
E) Enzyme catalyst
20. What carboxylic acid and alcohol are produced when ethyl propanoate undergoes acid-catalyzed hydrolysis?
A) Propanoic acid and ethanol
B) Ethanoic acid and propanol
C) Propanoic acid and methanol
D) Butanoic acid and ethanol
E) Formic acid and ethanol
21. Cysteine is a unique amino acid that contains which of the following atoms in its side chain?
A) a phenyl group
B) a heterocyclic ring
C) a sulfur atom
D) a sodium atom
E) a chlorine atom
22. The amine compound diethylamine ((CH3CH2)2NH) is classified as a ________.
A) tertiary amine
B) quaternary amine
C) secondary amine
D) primary amine
E) hydrated amine
23. What is the systematic IUPAC or common name of the tertiary amine (CH3)3N?
A) Trimethylamine
B) Ethyldimethylamine
C) Diethylamine
D) Ethylmethylnitride
E) Ethylmethylamine
24. A monosaccharide that consists of 6 carbon atoms, one of which is in an aldehyde group, is classified as a(n) ________.
A) aldopentose
B) aldohexose
C) aldotetrose
D) ketopentose
E) ketotetrose
CHEM 1406 | Exam 4 Review Package Page 3 of 4
Organic Chemistry & Biochemistry Practice Exam
PRACTICE TEST
25. The side chain of the basic amino acid lysine (-(CH2)4-NH3+) is classified as a ________ side chain.
A) basic
B) neutral
C) acidic
D) nonpolar
E) polar
26. Hemoglobin, a critical globular protein that carries and transports oxygen molecules throughout the bloodstream, is classified as a ________ protein.
A) transport
B) catalytic
C) structural
D) hormone
E) storage
27. Although twenty standard amino acids share a common backbone, they differ completely from one another in their ________.
A) ammonium group
B) R group
C) carboxylate group
D) alpha carbon
E) hydrogen bonding
28. The sweetest of all natural monosaccharides, also known commonly as fruit sugar, is ________.
A) galactose
B) fructose
C) sucrose
D) glucose
E) lactose
29. Hyperglycemia is a clinical condition in which ________.
A) the glucose level in the blood is higher than normal
B) the glucose level in the pancreas is higher than normal
C) the amount of glucose in the urine is lower than normal
D) the glucose level in the blood is about 100 mg/dL
E) the glucose level in the blood is lower than normal
30. In the pentapeptide GYKLA (Gly-Tyr-Lys-Leu-Ala), the C-terminus amino acid is ________.
A) alanine
B) glycine
C) lysine
D) leucine
E) tyrosine
31. In the D-isomer of a Fischer projection of a monosaccharide, the -OH group furthest from the carbonyl group is written ________.
A) on the left of the top chiral carbon
B) on the left of the bottom chiral carbon
C) on the right of the bottom chiral carbon
D) on the left of the middle chiral carbon
E) on the right of the top chiral carbon
CHEM 1406 | Exam 4 Review Package Page 4 of 4
Q9: [B] 4-chloropentanoic acid — Systematically numbering from the high-priority carboxylic acid carbon (C1) down the 5-carbon parent chain puts the chlorine substituent at Carbon-4. Hence, the systematic IUPAC name is 4-chloropentanoic acid.
Q10: [B] Benzoic acid — An aromatic carboxylic acid consists of a carboxylic acid functional group (-COOH) bound directly to a resonant benzene ring, which structurally defines benzoic acid (C6H5-COOH).
Q11: [D] Carboxylate group — Acidic amino acids (aspartate and glutamate) feature a carboxylic acid on their side chain. Under physiological conditions, these groups are ionized to form a negatively charged carboxylate group (-COO-).
CHEM 1406 | Exam 4 Review Package Page 1 of 4
Practice Exam Answer Key & Extensive Rationales
DETAILED KEY
Q12B
Q13B
Q14C
Q15A
Q16B
Q17C
Q18D
Q19C
Q20A
Q21C
Q22C
Q12: [B] Sodium benzoate and methylamine — Base hydrolysis of an amide (using NaOH) is irreversible and yields a carboxylic acid salt and a free neutral amine. Thus, hydrolysis of N-methylbenzamide produces sodium benzoate (C6H5-COO- Na+) and neutral methylamine (CH3-NH2).
Q13: [B] CH3-CH2-COO- Na+ — Sodium propanoate is an ionic carboxylate salt. Ionic substances dissociate completely into hydrated ions in water, yielding water solubility values that vastly exceed those of polar organic molecules like alcohols or neutral esters.
Q14: [C] Salt bridges — Non-covalent attractions that occur between ionic oppositely-charged side chains in a protein are known as salt bridges. The electrostatic attraction between a negatively charged carboxylate and a positively charged ammonium is a hallmark salt bridge.
Q15: [A] alpha (α) — In the cyclic ring structure of D-glucose, Carbon-1 (the anomeric hemiacetal carbon) has two possible stereocenters: if the anomeric hydroxyl group (-OH) is pointing DOWN, it is the alpha (α) anomer. If pointing UP, it is beta (β).
Q16: [B] Y — The systematic biochemically accepted one-letter abbreviation for the aromatic amino acid tyrosine is Y. (W represents tryptophan, T represents threonine, P represents proline, and R represents arginine).
Q17: [C] Enantiomers — Isomers that are related as non-superimposable mirror images of one another are explicitly defined as enantiomers. Diastereomers (B) are stereoisomers that are not mirror images of each other.
Q18: [D] backbone hydrogen bonding — Secondary structures (including both α-helices and β-pleated sheets) are completely stabilized by regular hydrogen bonds occurring strictly along the peptide backbone (between carbonyl oxygens and amide hydrogens).
Q19: [C] Protein — A peptide containing up to 50 amino acids is usually referred to as a polypeptide. Once the length exceeds 50 amino acids and the structure takes on a distinct folding pattern and definitive biological role, it is classified as a protein.
Q20: [A] Propanoic acid and ethanol — The hydrolysis of ethyl propanoate breaks the single C-O bond. The propanoate acyl group gets a hydroxyl group from water to form propanoic acid, while the ethyl portion forms ethanol.
Q21: [C] a sulfur atom — Cysteine contains a highly reactive thiol group (-SH) which contains a sulfur atom. Two neighboring cysteine residues can undergo oxidation to form a covalent disulfide linkage, crosslinking polypeptide chains.
Q22: [C] secondary amine — Diethylamine contains a nitrogen atom bonded directly to two separate ethyl carbon substituents and one hydrogen atom. Primary amines are bonded to one carbon group, tertiary to three, and quaternary to four.
CHEM 1406 | Exam 4 Review Package Page 2 of 4
Practice Exam Answer Key & Extensive Rationales
DETAILED KEY
Q23A
Q24B
Q25A
Q26A
Q27B
Q28B
Q29A
Q30A
Q31C
Q23: [A] Trimethylamine — The compound (CH3)3N consists of three identical methyl group carbon substituents covalently bonded to a single nitrogen atom. This fits the definition of trimethylamine.
Q24: [B] aldohexose — A monosaccharide containing an aldehyde group (represented by `aldo-`) and consisting of exactly 6 carbon atoms (represented by `hexose`) is systematically classified as an aldohexose (e.g., glucose).
Q25: [A] basic — Lysine's side chain (-(CH2)4-NH3+) contains a positively-charged protonated alkyl amine (ammonium group) at physiological pH, classifying it chemically as a basic side chain.
Q26: [A] transport — Hemoglobin is a globular metalloprotein found in erythrocytes that binds oxygen in the lungs and transports it to respiring biological tissues. This defines its role as a transport protein.
Q27: [B] R group — All twenty standard amino acids share a common alpha-carbon backbone with a carboxyl group, amine group, and hydrogen. They differ solely in the specific molecular structure of their R group (side chain).
Q28: [B] fructose — Fructose is a ketohexose that occurs naturally in fruits and honey. Structurally, it is the sweetest of all standard carbohydrates, significantly sweeter than glucose or sucrose.
Q29: [A] blood glucose higher than normal — Hyperglycemia refers to pathologically elevated concentrations of glucose circulating in the blood (typically above 130 mg/dL fasting), commonly linked with untreated diabetes mellitus.
Q30: [A] alanine — By IUPAC convention, peptide sequences are written starting with the free amine terminus (N-terminus) on the left and ending with the free carboxylate terminus (C-terminus) on the right. In GYKLA, alanine is on the far right.
Q31: [C] on the right of the bottom chiral carbon — In the D-isomer configuration of a carbohydrate Fischer projection, the hydroxyl group (-OH) bound to the chiral carbon furthest from the carbonyl group is oriented pointing to the right.
CHEM 1406 | Exam 4 Review Package Page 3 of 4
Step-by-Step Walkthroughs for Crucial Chemistry Concepts
CHEM 1406
In original Question 8, option D is identified as chiral. Let's analyze why: The carbon atom is bonded to four distinct groups: a methyl group (-CH3), a hydroxyl group (-OH), a hydrogen atom (-H), and a chlorine atom (-Cl). Because these four groups are completely distinct, the molecule lacks an internal mirror plane, rendering the molecule chiral. Options A, B, C, and E fail because they contain duplicate groups (such as multiple hydrogens or duplicate chlorines) on their central carbons.
Original Question 12 asks for the hydrolysis products of benzanilide under basic conditions (NaOH). Under basic conditions, the amide bond is cleaved to form a carboxylate salt and a neutral amine: Amide + NaOH → Sodium Carboxylate Salt + Amine For benzanilide (N-phenylbenzamide), cleavage of the carbonyl-nitrogen bond results in sodium benzoate (the sodium salt of benzoic acid) and neutral aniline (phenylamine). In an acidic environment, you would instead obtain carboxylic acid and anilinium chloride.
Original Question 3 asks for the ionized form of serine. Serine has the polar neutral side chain -CH2-OH. Under physiological conditions: The carboxylic acid group (normally -COOH) has a low pKa (~2) and is fully deprotonated into -COO-. The amine group (normally -NH2) has a high pKa (~9.5) and is protonated to -NH3+. The side chain -CH2-OH does not ionize. This results in the correct zwitterion structural formula shown in Option D.
CHEM 1406 | Exam 4 Review Package Page 4 of 4
