Problem 6 Atomic and molecular orbitals - PianetaChimica.it

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33 rd International Chemistry Olympiad ∗ Preparatory ProblemsPeak positions and relative intensities of individual lines in the 1 H NMRspectrum (400 MHz) of BLine (ppm) RelativeintensityLine (ppm) Relativeintensity1 6.535 1 8 3.870 12 6.505 1 9 3.525 13 6.495 1 10 3.505 14 6.465 1 11 3.495 15 3.930 1 12 3.475 16 3.910 1 13 3.000 127 3.890 1a. Label the unknown compounds in the bottles with IUPAC names, using theNMR spectra given in the figure.b. In the 1 H-NMR spectrum of B, assign the peak positions to specific protons.c. Calculate the spin-spin coupling constants for protons of compound B.d. Convert the peak positions of the first four lines into Hz (refer to theTable).What will be the peak positions of these lines in Hz, if the spectrum isrecorded on a 600 MHz instrument?e. Draw the possible structure of Meldrum's acid.f. Meldrum's acid has pK a = 4.83. Explain the acidity of Meldrum’s acid.g. Give the structure of the condensation product of Meldrum's acid with anaromatic aldehyde.2424Mumbai, India, July 2001
Problem 18 Polymer synthesis33 rd International Chemistry Olympiad ∗ Preparatory ProblemsEthylene finds extensive application in the manufacture of polymers and bulkchemicals. It is produced on a large scale by thermal and catalytic cracking ofalkanes obtained from natural gas and petroleum.In the presence of silver catalyst, ethylene reacts with oxygen to give P. CompoundP on heating with acidified water forms Q. 1 H-NMR spectrum of P has only onesignal while that of Q contains two signals.a. Identify and draw the structures for compounds P and Q.Compound R is obtained when P and Q react with each other. R reacts with SOCl 2to give S. On heating with alcoholic KOH, S gives T, an anaesthetic under the name"vinethene".PSOCl 2alc.KOH+ QR S Tb. Identify compounds R, S and T.Another compound dimethyl benzene-1,4-bis(acetate) can be synthesised fromp-xylene. Such a synthesis requires use of proper reagents so that desiredintermediate compounds and the final product are obtained. Various intermediatecompounds obtained in the synthesis of dimethyl benzene-1,4-bis(acetate) alongwith their structures are shown below.COOHCOOCH 3CH 3CH 2BrCH 2CNCH 2CH 2??? ?????CH 3CH 2BrCH 2CNCH 2CH 2p-xyleneCOOHCOOCH 3Dimethyl benzene -1,4 -bisacetatec. Identify the reagents used in this synthesis of dimethyl benzene –1,4-bis(acetate).Mumbai, India, July25 25
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Problem 6 Atomic and molecular orbitals - PianetaChimica.it

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