Organic Compounds:I)rawing Structures
Objective: To gain familiarity with organicstructuresandbondingthroughthe useof
drawingmoleculestructures.
Why arethereso manyorganiccompounds?Thereasonis that carbonatomshavethe ability to
link to othercarbonatoms(concatenate)
to producechainsor rings of almostinfinite size. Otherelements
do not concatenate
nearly aswell, dueto suchfactorsaspoor orbital overlapand lonepair-lonepair
electronicrepulsions.Otherelementscan alsocombinewith carbonto form hetero-spicies,hydrogen,
oxrygen,nitrogen,sulfir andthe halogensaremostprevalent.
The purposeofthis exerciseis to help you visualizethe structureof organiccompoundsby
drawingstructuralformulasof the morecornmonorganictypes.
You shouldconsultyour textbookfor a morecompletetreament of the natureandformation of organic
systems.
I' Draw sawhorsestructuresof the straight-chainalkanesfrom methanethroughdecane.
Note that eachcarbonatom canrotateaboutits respectivecarbon-carbonbond.
a) Sketchthe methanemoleculeshowingthe tetrahedralnahre of the carbonatom.
b) Using sawhorseline structureso
sketchthe configurationof ethanethroughdecane.
You may omit the hydrogensfrom the sawhorsestructures.
c) Sketchthe sawhorsestructureof butanewhenyou orient the butanemodel so that
the methyl groupsare anti- to oneanother(with an angleof l80o betweenthem).
d) Now sketch the sawhorsestructureof butanewhenyou orient the butanemodel
sothat the methyl groupsareat an angleof 1200.
e) Next, draw a sawhorsestructureof butanewhenyou orient the butanemodel so
that the methyl groupsareat an angleof 60o.
f) Finally, draw a sawhorsestructureof butanewhenyou orient the butanemodel so
that the methyl groupsareeclipsedor at an angleof 0oto eachother.
g) Explain which configurationis the most stableconfigurationfor butane.
2. Draw sawhorse(line skeleton)structuresofthe five stnrcturalisomersof the hexane
molecule,Cotlr+. Undereachstructure,give the corect IUPAC narnefor eachstructure.
a)
b)
c)
d)
e)
3. Draw sawhorse(line skeleton)structuresfor eachof the following unsaturated
hydrocarbons:
a) l-hexene
b) trans-3-hexene
c) cis-3-hexene
d) cis-fans-2,6-octadiene
b) l-pentyne
c) 2-pentyne
4. a) Draw a ring structureof the aromaticcompoundbenzene,CoIIo. What accountsfor
the observedfactsthat measurement
of C-C bond distancein benzeneshowsthat all are
the samelength (1.397A) andthat the C-C bondanglesareall l20o?
b) Benzenewas at onetime usedextensivelyasa solvent. However,sinceit hasbeen
found to be carcinogenic,it haslargelybeenreplaceby toluene. Toluenecontainsan
aromaticring substitutedwith a methyl Soup andhasa molecularformula"CzHs. Draw
a possiblestructurefor toluene. Do you think this materialwould havea higher or lower
boiling point thanbenzene?Explain.
5. Draw structuresof the following aromatichydrocarbons.
a) chlorobenzene
b) l,2-chlorobenzene
d) 4-bromobenzoicacid
e) paraaminobenzoicacid
g) 1,3,5-trimethylbenzene h) 2,4,6-trinitrotoluene
c) 3-nitrobenzene
f) 4-nihophenol
i) meta-zylene
j) Draw two resonanceforms for naphthaleneusingthe Kekule type structures.
k) Therearethreedichlorobenzeneisomers. Draw them. Which onewould you expect
not to havea dipole moment?Explain.
l) Draw the structurefor cyclobutyne. Would you expectthe cyclobutynestructureto be
a stablecompound?Explain.
6. Draw strucflres forthe following functionalgoup compounds:
a) 2-butanone
b) 2-methyl-2-propanol
c) ethylpropanoate
d) l-aminohexaneor hexanarnine e) 2-bromopentane
f) butanoicacid
g) Ethyl alcohol is misciblewith waterin all proportions,whereasdiethyl etheris only
slightly solublein water. Draw structuresof the two moleculesandexplain.
h) Draw structuresfor acetone(2-propanone)andfonnaldehyde(methanal).What are
the bond ilgles aroundthe C=O carbonatomin eachof thesecompounds?
Would you expectthesecompoundsto be solublein water?Explain.
7. Draw structuralformulasforthe following:
a) hexnnal
b) 3-chloropentane
c) benzoicacid
d) methylethylether
e) ethylethanoate
f) 3-pentanone
g) 2-aminobutane
h) 2-propanol
i) butanamide
j) cis-3-pentene
k) 3-pentyne
l) cyclohexane