Download Bastin Exam #I Fall 2007 - Organic Chemistry and more Lecture notes Chemistry in PDF only on Docsity!
Bastin
Fall 2007
pts)ProvideLewisstructures for thefollowingmoleculesindicating all lonepairsand
formal charges(if any). Be sureto showthe 3-D structureof the overallmolecule.
a) CH3NCO
N
t\
rr_c_x)=c=cl,
o,f-
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+
b) cH3cN
l! } \
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ll
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c) CH3CHO
(_
nts) Phosgene,
ClrC=O, has a smallerdipole moment than formaldehyde,H'C=O, even
though it containselectronegative chlorine atomsin place of hydrogenatoms. Explain.
lO.n
r ,
\occ\
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ata
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or
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L-cr
b-A>
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cf
c-\
bo.\
't'+
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\
t \
l\ -g-q=g,
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t r
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ot
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Fall 2007
- (8 pts)Consider H2C=C=CHz.Whatis the hybridizationandgeometry at eachC? Indicate
the bondtypesfor eachof the carbon-carbonbonds.Drawthe molecule,showingthe overall
geometry andthep orbitalsthatoverlapto form the pi bonds.Is it conjugated?
S;tltl
,
:\1"
- (10 pts)We nowknowthatmethane hasa tetrahedralcoordinationgeometry but it mightjust
aswell be
squareplanar.Explainhowthefactthatthereexists
only onedichloromethane
compound
(CHrClr) arguesagainstthe squareplanarstructure.
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t
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Trs
nA-\e-r
Loh,cle
$^o-L
c.i: euc
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Fall 2007
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t*|--[,.:
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ft
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7) (8pts)Anelectron
spin,.;inr, ,3i*ffi
uJtnrnument
tharcanrerrwhat
fracrion
of
thetimean unpairedelectron is foundat variousplaiesin a molecule.
Forthebenzyiradical
(C6H5CHz'), thereis a lot of unpaired electronduisi-ty at thecarbonpositions markri Uy
arrowsbelow. Useresonance structuresto
justify
thisresult.
- (8 pts)The arrowsin thefollo.wing diagrams showdifferentkindsof relationships for
benzene
(lefp-andcyclobutadiene (rigtrt). Predict
thecarbon/carbon bondlengthsin each
c.omPo-und..
.You_c,a
placenumbers
directly
9n lhe
structural
$iagrams.A typ-ical
C{
singlebondis 1.54Aanda typical c=c double bondis 1.42A.
r
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