DAT (Dental Admission Test) Organic Chemistry Flashcards

24 sample cards from the Organic Chemistry deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. Compare Markovnikov versus anti-Markovnikov addition to an alkene.

   Markovnikov: H adds to the carbon with more hydrogens; the electrophile/positive part adds to give the more stable carbocation. Anti-Markovnikov (e.g., HBr with peroxides/radicals): reversed regiochemistry.

2. What product and stereochemistry result from catalytic hydrogenation of an alkene?

   Syn addition of H2 across the double bond (both H atoms add to the same face) to give the alkane, using Pt/Pd/Ni catalyst.

3. What does hydroboration-oxidation (BH3 then H2O2/OH-) accomplish?

   Anti-Markovnikov, syn addition of water across an alkene to give an alcohol (OH on the less substituted carbon).

4. What does oxymercuration-demercuration achieve regiochemically?

   Markovnikov addition of water (OH on more substituted carbon) with no carbocation rearrangement.

5. Rank carbocation stability and name the stabilizing effects.

   Stability: allylic/benzylic ~ tertiary > secondary > primary > methyl; stabilized by hyperconjugation, inductive electron donation from alkyl groups, and resonance (allylic/benzylic).

6. Rank free-radical stability.

   Tertiary > secondary > primary > methyl (same trend as carbocations; stabilized by hyperconjugation and induction).

7. Why are carbanion stabilities opposite to carbocations regarding alkyl substitution?

   Carbanions bear a negative charge, so electron-donating alkyl groups destabilize them: methyl > primary > secondary > tertiary in stability.

8. What is the general formula for an acyclic alkene and an alkyne?

   Alkene (one C=C): CnH2n; alkyne (one C triple bond C): CnH2n-2.

9. What reagent set ozonolysis uses and what it produces from an alkene?

   O3 followed by reductive workup (Zn/H2O or DMS) cleaves C=C to give two carbonyl compounds (aldehydes/ketones); oxidative workup gives carboxylic acids/ketones.

10. How are terminal alkynes distinguished chemically from internal alkynes?

    Terminal alkynes have an acidic sp C-H (pKa ~25) that can be deprotonated by strong base (e.g., NaNH2) to form an acetylide nucleophile; internal alkynes cannot.

11. What is the product of oxidation of a primary alcohol with PCC versus with strong oxidants like KMnO4/Jones?

    PCC (mild) gives an aldehyde; strong oxidants (KMnO4, CrO3/H2SO4) give a carboxylic acid. Secondary alcohols give ketones; tertiary alcohols do not oxidize.

12. How does the Williamson ether synthesis form an ether?

    An alkoxide (R-O-) performs an SN2 attack on a primary alkyl halide; use the less hindered halide to avoid elimination.

13. Describe nucleophilic addition to a carbonyl by a Grignard reagent and the typical products.

    The carbanion-like R-MgX adds to C=O; after acid workup: formaldehyde gives a primary alcohol, other aldehydes give secondary alcohols, ketones give tertiary alcohols, esters give tertiary alcohols (with two R added).

14. What is keto-enol tautomerism and which form usually predominates?

    Equilibrium between a keto form (C=O with alpha C-H) and an enol form (C=C-OH); the keto form usually predominates because it is more stable.

15. What is the product of an aldol condensation?

    An enolate adds to a carbonyl to give a beta-hydroxy aldehyde/ketone (aldol), which on heating/dehydration gives an alpha,beta-unsaturated carbonyl (enone).

16. State Huckel's rule for aromaticity.

    A planar, cyclic, fully conjugated ring is aromatic if it contains 4n+2 pi electrons (n = 0,1,2,...); 4n pi electrons makes it antiaromatic.

17. In electrophilic aromatic substitution, classify ortho/para directors versus meta directors.

    Ortho/para directors are usually activating, electron-donating groups (e.g., -OH, -NH2, -OR, alkyl; halogens are o/p directing but deactivating). Meta directors are deactivating, electron-withdrawing groups (e.g., -NO2, -C=O, -SO3H, -CN).

18. Name the key electrophilic aromatic substitution reactions of benzene.

    Halogenation (X2/FeX3), nitration (HNO3/H2SO4), sulfonation (SO3/H2SO4), Friedel-Crafts alkylation (RX/AlCl3), and Friedel-Crafts acylation (RCOCl/AlCl3).

19. In retrosynthetic analysis, what is a disconnection and a synthon?

    A disconnection is the conceptual breaking of a bond to work backward from product to precursors; synthons are the idealized fragments (often charged) whose real reagent equivalents are used in synthesis.

20. In IR spectroscopy, what approximate absorptions identify O-H, C=O, and C triple-bond C/N?

    O-H: broad ~3200-3550 cm-1 (carboxylic acid even broader ~2500-3300); C=O: strong sharp ~1700 cm-1; C triple bond: ~2100-2260 cm-1.

21. In 1H NMR, what do chemical shift, integration, and splitting (n+1 rule) tell you?

    Chemical shift indicates the electronic/chemical environment (deshielding), integration gives the relative number of protons, and the n+1 rule gives the number of neighboring nonequivalent protons (multiplicity).

22. What does the molecular ion peak (M+) in mass spectrometry represent, and what is the M+2 clue for bromine/chlorine?

    M+ gives the molecular weight of the compound. A roughly 1:1 M:M+2 ratio indicates bromine; a roughly 3:1 M:M+2 ratio indicates chlorine.

23. In extraction (a key lab technique), how do you separate a carboxylic acid from a neutral organic compound?

    Wash the organic layer with aqueous base (NaHCO3/NaOH) to deprotonate the acid into a water-soluble carboxylate salt; it moves to the aqueous layer, leaving neutral compounds in the organic layer; then acidify to recover the acid.

24. What separation principle do distillation and recrystallization rely on?

    Distillation separates liquids by differences in boiling point (vapor pressure); recrystallization purifies solids based on differential solubility (compound soluble when hot, crystallizes pure when cold while impurities stay in solution).

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