13.1. Formulas, functional groups and the naming of organic compounds
A subsection of Chemistry, 9701, through 13. An introduction to AS Level organic chemistry
Listing 10 of 266 questions
Each of the three organic compounds, V, W, and X, has the empirical formula CH2O. The number of carbon atoms in each of their molecules is shown in the table. compound number of C atoms V W X V gives a brick red precipitate when warmed with Fehling’s reagent; W and X do not. W is a fruity smelling liquid. In X, the carbon atoms are bonded directly to one another. X gives an effervescence when shaken with Na2CO3; V and W do not. Give the structural formula of V. What functional group is present in W? Give the structural formula of W. When X is heated under reflux with acidified K2Cr2O7, the product, Y, gives no reaction with 2,4-dinitrophenylhydrazine reagent. Give the structural formula of X. Give the structural formula of Y, the compound formed from X. When X is warmed with a little concentrated sulfuric acid, a small amount of a cyclic compound, Z, is formed. Z has the molecular formula C6H8O4. Suggest a displayed formula for Z. What type of reaction occurs when Z is formed from X?
9701_w11_qp_23
THEORY
2011
Paper 2, Variant 3
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Compound C has the molecular formula C7H14O. Treating C with hot concentrated acidified KMnO4produces two compounds, D, C4H8O, and E, C3H4O3. The results of four tests carried out on these three compounds are shown in the following table. test reagent result of test with compound C compound D compound E Br2decolourises no reaction no reaction Nafizzes no reaction fizzes I2+ OH–no reaction yellow precipitate yellow precipitate 2,4-dinitrophenylhydrazine no reaction orange precipitate orange precipitate State the functional groups which the above four reagents test for. Br2NaI2+ OH–2,4-dinitrophenylhydrazine Based upon the results of the above tests, suggest structures for compounds D and E. D, C4H8O E, C3H4O3 Compound C exists as two stereoisomers. Draw the structural formula of each of the two isomers, and state the type of stereoisomerism involved. type of stereoisomerism
9701_w11_qp_41
THEORY
2011
Paper 4, Variant 1
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Compound C has the molecular formula C7H14O. Treating C with hot concentrated acidified KMnO4produces two compounds, D, C4H8O, and E, C3H4O3. The results of four tests carried out on these three compounds are shown in the following table. test reagent result of test with compound C compound D compound E Br2decolourises no reaction no reaction Nafizzes no reaction fizzes I2+ OH–no reaction yellow precipitate yellow precipitate 2,4-dinitrophenylhydrazine no reaction orange precipitate orange precipitate State the functional groups which the above four reagents test for. Br2NaI2+ OH–2,4-dinitrophenylhydrazine Based upon the results of the above tests, suggest structures for compounds D and E. D, C4H8O E, C3H4O3 Compound C exists as two stereoisomers. Draw the structural formula of each of the two isomers, and state the type of stereoisomerism involved. type of stereoisomerism
9701_w11_qp_42
THEORY
2011
Paper 4, Variant 2
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Different analytical techniques are used to build up a picture of complex molecules. Each technique on its own provides different information about complex molecules but together the techniques can give valuable structural information. Complete the table, identifying the technique which can provide the appropriate structural information. structural information analytical technique three-dimensional arrangement of atoms and bonds in a molecule chemical environment of protons in a molecule identity of amino acids present in a polypeptide One general method of separating organic molecules is chromatography. Briefly explain the chemical principles involved in each of the following techniques. paper chromatography thin-layer chromatography A combination of mass spectrometry and NMR spectroscopy is often enough to determine the structure of a simple organic compound. The organic compound N produced a mass spectrum in which the ratio of the M:M+1 peaks was 5.9:0.20, and which had an M+2 peak of similar height to the M peak. Calculate how many carbon atoms are present in one molecule of N. Deduce which element, other than carbon and hydrogen, is present in N. Explain how many atoms of this element are present in one molecule of N. The NMR spectrum of N is shown. 1H multiplet 6H doublet chemical shift, ppm absorption of energy State the empirical formula of N and, using the NMR data, suggest the structural formula of N, explaining your reasons.
9701_w11_qp_43
THEORY
2011
Paper 4, Variant 3
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Compound G is a naturally occurring aromatic compound that is present in raspberries. HO O compound G Identify the functional groups present in compound G. Complete the following table with information about the reactions of the three stated reagents with compound G. reagent observation structure of organic product type of reaction sodium metal aqueous bromine aqueous alkaline iodine The dye H can be made from compound G by the route shown below. J K step 1 step 2 compound G dye H HO N SO3H N O Draw the structures of the amine J and the intermediate K in the boxes above. Suggest reagents and conditions for step 1, step 2. Suggest a reaction scheme by which compound G and propanoic acid could be converted into compound L. compound L O O O
9701_w12_qp_41
THEORY
2012
Paper 4, Variant 1
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Compound G is a naturally occurring aromatic compound that is present in raspberries. HO O compound G Identify the functional groups present in compound G. Complete the following table with information about the reactions of the three stated reagents with compound G. reagent observation structure of organic product type of reaction sodium metal aqueous bromine aqueous alkaline iodine The dye H can be made from compound G by the route shown below. J K step 1 step 2 compound G dye H HO N SO3H N O Draw the structures of the amine J and the intermediate K in the boxes above. Suggest reagents and conditions for step 1, step 2. Suggest a reaction scheme by which compound G and propanoic acid could be converted into compound L. compound L O O O
9701_w12_qp_42
THEORY
2012
Paper 4, Variant 2
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Questions Discovered
266