MDCAT Chemistry chapter 13: Chemistry · Fundamental principles of organic chemistry MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
39 exam-style questions on Chemistry · Fundamental principles of organic chemistry, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Bonding and reactivity in carbon compounds10 questions
Ten Chemistry · Fundamental principles of organic chemistry questions with answers
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. In the solid state, glycine, NH2CH2COOH, exists mainly as +H3N–CH2–COO−. This form arises because
A
a proton moves from the –NH2 group to the –COOH group of the same molecule
B
two glycine molecules join together with the loss of a water molecule
C
an electron moves from the –COOH group to the –NH2 group of the same molecule
D
a proton moves from the –COOH group to the –NH2 group of the same molecule
Show answer
Answer: D. The acidic –COOH group gives H+ to the basic –NH2 group within the same molecule, forming a dipolar ion (zwitterion), an internal salt. Joining two molecules with loss of water makes a dipeptide instead.
2. How many sp2 hybridised carbon atoms are there in but-3-enal, CH2=CH–CH2–CHO?
A
2
B
4
C
1
D
3
Show answer
Answer: D. The two C=C carbons and the carbonyl (C=O) carbon each form three σ bonds and one π bond, so they are sp2; the CH2 between them has four single bonds and is sp3. Overlooking the C=O carbon gives 2.
3. Counting cis and trans forms separately, how many alkenes have the molecular formula C4H8?
A
3
B
4
C
5
D
2
Show answer
Answer: B. But-1-ene, cis-but-2-ene, trans-but-2-ene and 2-methylpropene: four. Forgetting the cis-trans pair gives 3. Cyclobutane and methylcyclopropane are also C4H8 but are not alkenes.
4. Methane, the chief component of natural gas, is also called marsh gas because it
A
is produced when plant matter decays under water without air
B
is produced when plant matter burns in marshes in excess air
C
dissolves readily in marsh water and is released on warming
D
is produced by cracking petroleum found under marshy land
Show answer
Answer: A. Bacteria break down dead plant material in the absence of air in swamps and marshes, releasing methane. Burning in excess air gives carbon dioxide and water, and methane is almost insoluble in water.
5. Which pair of compounds are isomers of each other?
A
methyl methanoate and propanoic acid
B
propanone and propan-2-ol
C
methyl ethanoate and propanoic acid
D
propanal and propan-1-ol
Show answer
Answer: C. Methyl ethanoate, CH3COOCH3, and propanoic acid, CH3CH2COOH, are both C3H6O2 with different structures. In each other pair the molecular formulae differ, by CH2 or by two hydrogen atoms.
6. The compound CH3–S–CH2CH3 belongs to which class of organic compounds?
A
a thiol (thioalcohol)
B
a thioether (sulphide)
C
an ether
D
a sulphonic acid
Show answer
Answer: B. A sulphur atom joining two alkyl groups makes a thioether (sulphide), the sulphur analogue of an ether. A thiol needs a hydrogen atom on sulphur, –SH.
7. Position isomerism of the functional group is impossible in which homologous series?
A
alkanals (aldehydes)
B
alkanols (alcohols)
C
alkanones (ketones)
D
alkenes
Show answer
Answer: A. The –CHO carbon can bond to only one other carbon, so the group is always at the end of the chain (C-1). Alcohols (propan-1-ol, propan-2-ol), ketones (pentan-2-one, pentan-3-one) and alkenes (but-1-ene, but-2-ene) all have position isomers.
8. How many primary, secondary, tertiary and quaternary carbon atoms, in that order, are there in 2,2,4-trimethylpentane, (CH3)3C–CH2–CH(CH3)2?
A
4, 2, 1, 1
B
5, 2, 1, 0
C
5, 1, 1, 1
D
3, 2, 2, 1
Show answer
Answer: C. The five CH3 groups are primary, the CH2 is bonded to two carbons (secondary), the CH is bonded to three (tertiary) and the carbon carrying three methyl groups is bonded to four (quaternary).
9. A carbon atom in an alkane is called tertiary (3°) when it is
A
bonded directly to three hydrogen atoms
B
the third carbon atom from the end of the chain
C
bonded directly to four other carbon atoms
D
bonded directly to three other carbon atoms
Show answer
Answer: D. Carbon atoms are classed by how many other carbon atoms they are directly bonded to: one (primary), two (secondary), three (tertiary) or four (quaternary). A carbon carrying three hydrogens is an end CH3 group, which is primary.
10. Which compound has a metamer?
A
dimethyl ether, CH3OCH3
B
propanone, CH3COCH3
C
diethylamine, (C2H5)2NH
D
butanal, CH3CH2CH2CHO
Show answer
Answer: C. Diethylamine and methylpropylamine, CH3NHC3H7, have the same –NH– group with different alkyl groups on each side. Dimethyl ether and propanone are the smallest members of their classes, so their carbons cannot be shared out differently, and aldehydes have a monovalent group that cannot show metamerism.
Chemistry · Fundamental principles of organic chemistry: questions students ask
How many Chemistry · Fundamental principles of organic chemistry MCQs are there?
39, each with the answer and a short explanation, across 2 topics: Classification and isomerism, Bonding and reactivity in carbon compounds. Every chapter test draws ten of them, so you can take it many times.
Is the MDCAT Chemistry chapter 13 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
