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MCAT Organic Chemistry Study Questions

These are questions I came up with when I was studying for the MCAT.

On this page:

bulletGeneral Concepts
bulletTrends, Stabilities, etc.
bulletAnalysis and Separations
bulletStereochemistry
bulletAlkanes
bulletAlkenes
bulletAlkyl Halides
bulletBenzene & co.
bulletAlcohols and Ethers
bulletAldehydes and Ketones
bulletCarboxylic acids and derivatives
bulletAmines
bulletBiomolecules
bulletMiscellaneous

 

General Concepts

 

  1. What is the difference between hydride and a "proton"?
  2. What is an atomic orbital?  What is a hybrid orbital?  What is a molecular orbital?
  3. How many electrons is represented in a single bond?  What type of molecular orbital is a single bond?
  4. Which hybrid orbital type has the most "s" character?
  5. In a normal organic molecule, how many lone pairs of electrons does carbon have?  oxygen? nitrogen?  a halide?
  6. What is the difference between chlorine and chloride?  In what phase is chlorine normally found?  Chloride?  Bromine?  Bromide?  Iodine?  Iodide?
  7. Which element has the highest electronegativity?
  8. In order to be a hydrogen bond donor, a molecule must have a hydrogen connected to any of what three elements?
  9. What atoms in an organic molecule can serve as hydrogen bond acceptors?
  10. What molecular orbitals are involved in a double bond?  Which of the two is the weakest?
  11. What is the difference between INDUCTION and RESONANCE?

 

 

 

Trends, Stabilities, etc.

 

  1. Do radical stability trends mirror carboanions or carbocations?
  2. Which are the most stable carbocations?  Why?  Which are the lowest energy carbocations?  Which are the highest energy carbocations?
  3. Which tends to be more stable : a cis alkene or a trans alkene?
  4. Which tends to be more stable : a tetrasubstituted alkene or a monosubstituted alkene?
  5. Does higher BP mean it is more likely or less likely to be in a condensed phase (solid/liquid) at room temperature?
  6. Does higher MP mean it is more likely or less likely to be in a fluid phase (liquid/gas) at room temperature?
  7. What factor(s) is the BP of an organic substance usually based on?
  8. What factor(s) is the MP of an organic substance usually based on? 
  9. Shorter hydrocarbon chain vs. longer hydrocarbon chain : which has the highest BP?  Why? Which is usually the least water soluble?  Why?
  10. Less branched hydrocarbon vs. more branched hydrocarbon (equal MW) : which has the highest BP?  Why?
  11. Increasing the unsaturation (double bond number) of a long alkane does what to its melting point?  How does this apply to fatty acids?
  12. In cyclohexane, which is the more stable substituent position : axial or equatorial?  Why?
  13. In a carboxylic acid, how do electron-withdrawing groups affect the acidity of the molecule?
  14. How does branching affect the melting point of a compound?
  15. What is the approximate pKa of a carboxylic acid?  Of a phenol?  Of an alcohol?  Of water?  According to the pKa value, which is more acidic?
  16. How do amines and amides differ in basicity?

 

 

Analysis and Separations

 

  1. In mass spec., what is the molecular ionBase peakParent peak?
  2. What is meant by a mass-to-charge ratio?  What does mass spectroscopy sense?  What is most common charge on these molecules?  Is an uncharged molecule recorded?
  3. In mass spectroscopy, why does a peak that corresponds to a MW one or two greater than the parent peak sometimes occur?
  4. What solvent is commonly used in proton NMR?  Why is this solvent used?  What reference molecule is commonly used?
  5. In NMR, what side is "downfield"?  What side is "upfield"?  Which side corresponds to absorption at a higher energy?
  6. Does NMR involve electron spin or nuclear spin?  What is the difference?
  7. In NMR, what is a chemical shift?  On what axis in chemical shift measured?
  8. What is spin-spin splitting?  Why does it occur?
  9. What is mean by "equivalent" hydrogens?  Is the hydrogen "cis" over a double bond equivalent to a hydrogen "trans" over that double bond?  How many peaks would be caused by three isolated (no spin-spin splitting) , equivalent hydrogens?
  10. In NMR, what happens to the chemical shift when an atom is "deshielded"?  What might cause this deshielding?
  11. What isotype of carbon is sensed in carbon-NMR?  What type of carbon is used in radioactive dating?
  12. In NMR, what is measuring the area underneath the peaks called?  What does this tell you?  Does this indicate the total number of atoms?
  13. How do protons bonded to nitrogen or oxygen appear on H-NMR?  What is meant by "exchange"?
  14. What is the typical chemical shift of aromatic hydrogens?
  15. What does IR measure?  What must a molecule be if it is to be analyzed with IR?  What happens to the atoms in the molecule when exposed to IR frequencies?
  16. What is meant by wavenumber?  Is this proportional to wavelength?  Is this proportional to frequency?
  17. At what wave number is O-H found in IR spectra?  Is this broad or narrow?  What about the carbonyl group?
  18. What is UV spectroscopy?  What does it measure?  How does conjugation affect measurements?  What are the characteristics of an organic molecule that would absorb certain frequencies of visible light?  What do we call these molecules?
  19. What is TLC?  Of what polarity is the solid?  Of what polarity is the solvent?
  20. Which type of molecules move the furthest in TLC?  How is distance traveled expressed in TLC?
  21. What are extractions?  What two types of phases are used?
  22. If an organic molecule is water soluble after making the solution weakly acidic, it most likely contains what functional group?
  23. What types of molecules might be distinguished by whether they dissolve in a weak aqueous base or in a strong aqueous base?
  24. Molecules with a net charge will tend to dissolve in what type of solvent?
  25. What separation procedure separates a liquid from a liquid?  A solid from a liquid?
  26. What property difference is centrifugation (separation) based on?
  27. Why does distillation of a grain alcohol "quit working" at a certain concentration?  What term is used to describe the mixture at this point?

 

 

 

 

Stereochemistry

  1. What is meant by stereochemistry?  What is a stereoisomer?  What is meant by chirality?
  2. What is another name for geometrical isomer?
  3. What is a stereogenic center?
  4. What is the formula for the number of stereoisomers in a (non-meso) compound with n # of stereogenic centers?
  5. What is meant by the stereochemistry term meso?
  6. Can nitrogen atoms serve as a stereogenic centers? Do oxygen and nitrogen atoms contribute to chirality?
  7. What is the Cahn-Ingold-Prelog convention?  What is it used for?
  8. What is meant by configuration?  What is an absolute configuration?
  9. Does D- and L- convention indicate which way a biomolecule rotates light?  What about R- and S-?
  10. Does the (d) and (l) convention indicate which way a molecule rotates light? What about (+) and (-)?
  11. What is meant by "resolving entantiomers?"
  12. Can a molecule with stereogenic centers be achiral?  How or why not?
  13. What is a racemic mixture?  Which way does it rotate light?
  14. What properties of entantiomers are different?  Is the boiling point different?  Is the melting point different?
  15. During a reaction, what happens to the stereochemistry after a stereogenic center temporarily becomes a carbocation?

 

 

 

Alkanes

 

  1. What is meant by the letter "n-" preceding an alkane?  How is this different from capital "N-" preceding the chemical name?
  2. Which is more likely to be in the gas phase : propane or octane?   Where might we find each of these in everyday life?
  3. What is a conformational isomer?  What is the difference between configuration and conformation?
  4. Is it possible to isolate a conformer?  How or why not?
  5. What is a saw-horse diagram?  What is a Newman projection
  6. What is the staggered conformation?  What is the eclipsed conformation?  Gauche and anti are subtypes of which conformation? Which is the lowest in energy?  Which is the highest?
  7. Do the terms gauche and anti make any sense when talking about butane?  propane?  ethane?
  8. When discussing the boat and chair conformation, what molecule is usually being described?  Which conformation is lowest in energy?
  9. Under what circumstances can cis and trans describe an substituted alkane?
  10. What is meant by axial and equatorial?  Generally speaking, a substituted cyclohexane is lowest in energy when the substituent is in which orientation?
  11. What is the water-solubility of alkanes like?
  12. What alkane is the major component of natural gas? What alkane is found plastic cigarette lighters?
  13. Roughly how many carbons are in a typical "gasoline molecule"?
  14. What number of ring carbons provides the most stable cycloalkane formation?
  15. What is the typical bond angle of alkanes?

 

 

 

Alkenes

 

  1. How does the melting point of an alkene compare to that of an otherwise equivalent alkane?  What are unsaturated fats?  What are saturated fats?  Hydrogenation converts which to which?
  2. What is an addition reaction?  What is an elimination reaction?  What is a substitution reaction? 
  3. What is the difference between hydrogenation and hydration?  These are examples of which type of reaction?
  4. What type of molecule undergoes dehydration to form an alkene?  What type of molecule undergoes dehydrohalogenation to form an alkene?
  5. What is a hydroxylation reaction?  What is the product formed when an alkene is hydroxylated?
  6. What type of agent is potassium permanganate?  What happens when an alkene is reacted will cool, friendly KMnO4?  What about warm, angry KMnO4?
  7. What is meant by a reaction that proceeds in a Markovnikov fashion?
  8. What is the difference between the terms allylic and vinylic?
  9. What type of reaction (in broad terms) can be thought of as the conversion of a single bond to a double bond?

 

 

Alkyl Halides

  1. What is a synonym for alkyl halides?
  2. What is an organometallic compound?  What are some examples of types of organometallic compounds?
  3. What is an alkyllithium reagent?  What is a lithium diorganocopper reagent? "Whose" reagent is this?
  4. What is an organomagnesium halide reagent?  "Whose" reagent is this?  How does one form these reagents?
  5. What is a Walden inversion?  With what reaction is it associated?
  6. Which type of reaction is favored by heat : elimination or substitution?
  7. Of Sn1 and Sn2, which one takes place in one step?  Which one is unimolecular? 
  8. Of unimolecular and bimolecular, which type of reaction has a carbocation intermediate?
  9. In an nucleophilic substitution of alkyl halides, what generally serves as the electrophile?
  10. Primary alkyl halides tend to undergo which type of substitution- Sn1 or Sn2?  Tertiary?
  11. Of the four main types of alkyl halide reactions, which is associated with the term "anti periplanar"? 
  12. What type of molecule/atom tends to make the best leaving group?
  13. What is the better leaving group - F or I?  Which is the stronger acid : HF or HI?
  14. What is the difference between a protic and a polar-aprotic solvent?  Which reaction does each favor?

 

Benzene & co.

  1. What is the difference between cyclohexane and benzene?  What about the 3D shapes of each?
  2. What are electrophilic aromatic substitutions (EAS)?  Why substitution and not addition?
  3. Are halogen substituents meta-directing or ortho-para directing for EAS reactions?  Why?
  4. Are halogen substituents activating or deactivating (EAS)?  Why?
  5. What is Hckel's rule?
  6. What are the only ortho/para directing deactivators?
  7. If a substituted benzene molecule reacts (via EAS) to form a mixture consisting of about 62% Cmpd A and 32% Compound B, which position is represented by Cmpd A?  Cmpd B?
  8. What "proper name" describes reactions that add an alkyl group or an acyl group to benzene?  What lewis acid catalyst is used?
  9. What is the structure of toluene? of aniline? of cumene? of styrene?
  10. What is the difference between a phenyl- and a benzyl- substituent?
  11. What does TNT stand for? 

 

 

 

Alcohols and Ethers

  1. In an alcohol, what is the hybridization of the carbon that is bound to the hydroxyl group?  What about in phenols?
  2. What are the few reactions an ether can participate in?  Why are ethers so stable?
  3. What is a hemiacetal?  hemiketal?  acetal?  ketal?
  4. Analogy-  acetal : ketal :: aldehyde : ______ ?
  5. What is commonly formed by the (gradual) oxidation of ethanol?
  6. Where does oxidation of primary alcohols lead?  Secondary alcohols?
  7. What process converts a carboxylic acid into an alcohol?
  8. What is a gem-diol? 
  9. What is the structure of glycol?
  10. If one takes the proton off of an alcohol's oxygen, what is the resulting type of molecule called?  How would one get this proton off?

 

 

Aldehydes and Ketones

  1. What is the difference between an aldehyde and a ketone?
  2. Where does oxidation of an aldehyde lead? Why does the oxidation behavior of a ketone differ from that of an aldehyde?
  3. What is the chemical formula for acetone?  What is acetone commonly used for?
  4. What type of carbonyl reaction is characteristic of aldehyde/ketones?  Is the carbonyl group preserved?
  5. What is the structure of acetone?  benzaldehyde?
  6. Does hydrogen bonding take place between plain ole aldehydes?  ketones?

 

 

Carboxylic acids and derivatives

  1. What are the carboxylic acid derivatives (CADs)?  Name them in order from highest to lowest in terms of their position on "the reaction ladder".
  2. What reagent converts a carboxylic acid into its corresponding acid chloride? What converts a carboxylic acid into its acid bromide?
  3. What happens to the acidity of a carboxylic acid when electronegative groups are added to neighboring atoms? 
  4. What is the alpha position on a carboxylic acid?  The beta position?  The gamma position?
  5. What is saponification?  Does this occur under acidic or basic conditions?
  6. What are amides?  How does one form one from an acyl chloride?
  7. What type of carbonyl reaction is characteric of CADs (as opposed to that of ketones/aldehydes)?  Is the carbonyl preserved?

 

 

Amines et al.

  1. What is the difference between ammonia and ammonium?  Which is acidic and which is basic?
  2. Are amines basic?  Are amides basic?
  3. What is an imine?  What is an imide?
  4. What is the name(s) of the group consisting of a carbon with a triple-bond to a nitrogen atom?
  5. What is reductive amination?
  6. What is a Schiff base?
  7. What is a nitrile?  What is another name for these compounds?  What does reduction turn them into?
  8. What is a nitro group?  How are they converted into amino groups?
  9. What is the structure of hydrazine?

 

 

 

 

 

Biomolecules (also see Biochemistry in MCAT Biology Study Questions)

  1. What are the four main classes of biomolecules?
  2. Which class (or classes) of (simple) biomolecules contains sulfur? which contains nitrogen? oxygen?  phosphorus? 
  3. What is so special about proline?
  4. How many of the standard amino acids are achiral?
  5. What ratio of G:C or A:T will one find in a double stranded piece of DNA?  Will this hold for a single stranded piece?
  6. How does the number of stereogenic centers change when an acyclic sugar becomes cyclic?
  7. What is meant by mutarotation?  What is meant by anomer?
  8. What is meant by glycoside
  9. In sugars, what is the difference between an alpha and a beta linkage?  Which ones are more common (in food)?
  10. What is the difference between phosphorus and inorganic phosphate?  What about pyrophosphate?
  11. What is CTP?  UTP?  GTP?
  12. How does one specify the two different ends of a protein?  (__ terminus)
  13. In what order (by convention) are the amino acids in a protein written? 
  14. To what functional group do peptide bonds belong?  What about the glycerol-fatty acid linkages in fats?  What about glycosidic linkages?
  15. Why is D-fructose sometimes referred to as 'levulose'?
  16. Which of the L-amino acids has an alpha carbon with an absolute configuration R?

 

 

Miscellaneous

  1. Which is the stronger reducing agent : LAH or NaBH4?

 

 

 

 

 

 

 

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