Organic Chemistry 1 · Structure and electron accounting
Functional groups and connectivity: practice problems
39 problems, each with its worked solution. Open one to read every step, or filter by tag.
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- Acetate and carbonic acid from acetic acid and bicarbonate
- Tetrahydro-2H-pyran-2-ol from 5-hydroxypentanal
- Ethylammonium chloride from ethylamine and HCl
- 1-Ethoxyethanol: hemiacetal from acetaldehyde and ethanol
- Methoxy(phenyl)methanol: hemiacetal from benzaldehyde
- Phenoxide from phenol and aqueous sodium hydroxide
- Ethanethiolate from ethanethiol and hydroxide
Draw the mechanism 7
- Acetate and carbonic acid from acetic acid and bicarbonateDraw the proton transfer from acetic acid to bicarbonate and explain why a carboxylic acid fizzes with sodium bicarbonate while phenols and alcohols do not.
- Tetrahydro-2H-pyran-2-ol from 5-hydroxypentanalDraw the acid-catalysed ring closure of 5-hydroxypentanal to the cyclic hemiacetal tetrahydro-2H-pyran-2-ol and explain why the six-membered ring forms.
- Ethylammonium chloride from ethylamine and HClDraw the proton transfer from HCl to the nitrogen lone pair of ethylamine and explain why amines dissolve in aqueous acid as ammonium salts.
- 1-Ethoxyethanol: hemiacetal from acetaldehyde and ethanolDraw the three acid-catalysed steps that join acetaldehyde and ethanol into the hemiacetal 1-ethoxyethanol, and identify the new functional group.
- Methoxy(phenyl)methanol: hemiacetal from benzaldehydeDraw the acid-catalysed addition of methanol to benzaldehyde that gives the hemiacetal methoxy(phenyl)methanol, and recognise the carbon that carries both OH and OCH3.
- Phenoxide from phenol and aqueous sodium hydroxideDraw the proton transfer from phenol to hydroxide and use it to tell a phenol apart from an ordinary alcohol such as cyclohexanol.
- Ethanethiolate from ethanethiol and hydroxideDraw the proton transfer from ethanethiol to hydroxide and explain why a thiol is deprotonated almost completely by hydroxide while ethanol is not.
Predict the product 4
- A limited reactivity predictionPredict the initial electrophilic site from a functional-group map without overclaiming a full reaction.
- Highest-boiling C4H8O2 isomerPredict the highest-boiling compound among same-formula isomers from which one can donate hydrogen bonds.
- Which group names the suffix?Pick the functional group that takes the suffix in an IUPAC name.
- Molecular formula from a skeletal drawingConvert a skeletal structure into its molecular formula by counting implicit hydrogens.
Classify 5
- Which atom is beside the carbonyl?Classify an ester from its acyl connectivity.
- A tetrahedral carbon with two oxygensDistinguish acetal and hemiacetal patterns without invoking a carbonyl.
- Classify caprolactam: lactam or amine?Classify a ring containing N–H next to C=O as one amide group rather than two separate groups.
- Acid, ester and arene: functional groups of aspirinName every functional group in aspirin from its structure and avoid mistaking the ester carbonyl for a ketone.
- Match a name to a structureChoose the structure that matches an IUPAC name containing a functional-group suffix.
Compare 4
- Formula versus connectivityCompare constitutional isomers with different functional groups.
- Boiling points of four compounds near 74 g/molRank oxygen compounds of nearly equal molar mass by boiling point from the intermolecular forces their functional groups allow.
- Rank naming priority of five functional groupsOrder five common functional groups by IUPAC suffix priority to decide which one names a polyfunctional molecule.
- Rank water solubilityRank four-carbon compounds by water solubility from functional-group hydrogen bonding.
Calculate 8
- A formula constrains but does not identifyCalculate unsaturation and recognize the remaining connectivity ambiguity.
- Classify an amine by degreeClassify an amine as primary, secondary or tertiary by counting carbons on nitrogen.
- Degrees of unsaturation for C5H9NCalculate degrees of unsaturation for a nitrogen-containing formula, adding one hydrogen for each nitrogen.
- Degrees of unsaturation for C8H8O2 with a benzene ringCalculate degrees of unsaturation for an aromatic formula and account for each one with the benzene ring and a carbonyl.
- Count hydrogen-bond donorsCount the hydrogen-bond donor hydrogens in a drawn molecule.
- Spot the amide in acetaminophenPick the drawn molecule that contains both an amide and a phenol, as acetaminophen does.
- Count C3H6O isomers with C=OCount constitutional isomers of a formula that contain a carbonyl group.
- Count the C4H10O alcohols and ethersCount every constitutional isomer of a saturated C4H10O formula across both the alcohol and ether functional groups.
Find the error 2
- Identifying the triple-bond partnerDiagnose classification based on the identities of bonded atoms.
- Does acetone hydrogen-bond with itself?Diagnose a hydrogen-bonding claim by checking that a liquid has both a donor and an acceptor.
Interpret the evidence 3
- Two functional groups in one small moleculeInventory independent functional groups without merging distant atoms.
- Skeletal structure of CH3COCH2CH3Convert a condensed formula containing CO into the correct skeletal structure and functional group.
- Find the hemiacetal carbon in glucopyranoseLocate the hemiacetal carbon of a cyclic sugar by finding the carbon bonded to both an OH and the ring oxygen.
Work backward 2
- Reconstructing a named connectivity classRecover an amide structure from a local connectivity requirement.
- Which C3H6O2 structure is a carboxylic acid?Pick the carboxylic acid among same-formula isomers by finding OH bonded directly to the carbonyl carbon.
Plan a synthesis 2
- What additional observation is enough?Plan a connectivity distinction that atom counts cannot supply.
- Bicarbonate test: butanoic acid versus ethyl acetatePlan a one-reagent bench test that separates a carboxylic acid from an isomeric ester by acidity.
Explain why 2
- An oxygen without an O–H bondExplain why an oxygen-containing formula need not be an alcohol.
- Why carbon dioxide has no net dipoleExplain how molecular geometry decides whether polar bonds give a polar molecule, using carbon dioxide.
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