(a)Arrange the following alkenes in order of their relative stability. How will you proceed to determine the order practically? 1-hexene cis-3-hexene trans-3-hexene 2-methyl-2-pentene 2,3-dimethyl-2-butene [5]
(b)Explain why? Poly substitution is a complicating factor in aromatic alkylation but not in aromatic nitration or halogenation. A undergoes nitration predominantly at the ortho/para positions but B mainly at meta position. (A = benzene with –CH₂CH₂CN substituent; B = benzene with –HC=CHCN substituent) [5]
(d)Explain why? Tertiary carbocation is more stable than primary. Ethanol has higher boiling point than diethyl ether. [5]
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Q. 3
(a)Write the structural formula for more stable conformation of each of the following compounds: trans-1-Fluoro-3-methylcyclohexane cis-1-Iodo-4-methylcyclohexane cis-1-tert-Butyl-4-methylcyclohexane cis-1,3,5-Trimethylcyclohexane [8]
(b)Mention R & S configuration of the following compounds. (Three stereocentre structures shown involving OH, Cl, OCH₃, COOH, HOH₂C groups) [5]
(c)Draw and label the E and Z isomers for each of the following compounds. CH₃CH₂C(Cl)=CHCH₂CH₃ HOCH₂CH₂C(O=CH)(C(CH₃)₃)=C≡CHI CH₃CH₂CH₂CH₂C(CH₃)(CH₂Cl)=C(CHCH₃)(CH₃) CH₃CH₂CH=CHCH₃ [5]
(d)Draw the structure of (Z)-3-isopropyl-2-heptene. [2]
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Q. 4
(a)In benzaldehyde, two of the ring protons have resonance at 7.87 ppm, and the other three have resonance in the range from 7.5 to 7.6 ppm. Explain. [4]
(b)Arrange the following protons in the decreasing order of their δ values in ¹H-NMR and account for your order: Methyl, ethylenic, acetylenic, aryl and aldehydic. [4]
(c)List the solvents most commonly used in IR spectroscopy. Why are water and ethanol not suitable solvents? [4]
(d)The UV spectrum of acetone shows absorption maxima at 166, 189, and 279 nm. What type of transition is responsible for each of these bands? [4]
(e)What types of electronic transitions are possible for each of the following compounds? Cyclopentene Acetaldehyde Dimethyl ether Methyl vinyl ether [4]
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Q. 5
(a)Write down the reagents, conditions and mechanisms of the following reactions. Kolbe reaction Williamson synthesis Dow Process Reimer-Tiemann reaction Bromination of phenol [10]
(b)Outline all steps involved in the synthesis of the following compounds from benzene or toluene, assuming that the ortho/para mixtures are separable. n-Butylbenzene m-Nitrotoluene p-Bromonitrobenzene p-Bromobenzoic acid 1,2-Dibromo-4-nitrobenzene [10]
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Q. 6
(a)Describe with equations all possible methods that can be used for the preparation of n-hexane. [10]
(b)Why is the Corey-House Method more suitable as compared to the Wurtz reaction for the synthesis of alkane? Explain with examples. [5]
(c)Draw the structures of the following compounds and label them with IUPAC systematic rules. 3-cyclopentylhexane 2-cyclobutyl-3-methylpentane Isopropylcyclodecane 2-methylbicyclo[3.2.0]heptane 8-methylbicyclo[3.2.1]octane [5]
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Q. 7
(a)How can you prepare each of the following substances by a reaction involving Grignard reagent? (CH₃)₃COH (Two ways) Cyclopentanol (CHOH) CH₃CH₂CHOHCH₃ (Two ways) (CH₃)₃CD (CH₃CH₂)₃COH (Three ways) [5]
(b)How will you bring about the following conversions? → CH₃CH(COOC₂H₅)₂ CH₃CHBrCH₂COOC₂H₅ → HOOCH₂CH(CH₃)CH₂COOH → HOOCCH₂CH(CH₃)CH₂COOH [5]
(c)How would you synthesize each of the following compounds by the Reformatsky reaction? H₃C–CH₂–CH₂–C(OH)(CH₂CH₃)–CH₂–C=O type structure Related β-hydroxy ester/ketone structure [5]
(d)How would you synthesize each of the following compounds by the Wittig reaction? C₆H₅C(CH₃)=CH₂ C₆H₅CH=CHC₆H₅ [3]
(e)How will you synthesize each of the following substances by an acetoacetic ester synthesis? 3,4-dimethyl-2,5-hexanedione 3-acetyl-5-hexanoic acid [2]
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Q. 8
(a)Discuss the following topics. Prostaglandins Terpenes [12]
(b)Name the epimers of D-glucose. [4]
(c)Clearly represent the most stable conformation of the α-pyranose form of each of the following sugars. D-Galactose D-Mannose L-Mannose L-Ribose [4]
The 2023 CSS Chemistry paper set by the Federal Public Service Commission. Question wording only; questions marked “Not yet checked” have not been compared with the official paper yet. Open the official paper beside the questions to check any of them.
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