15.1. Halogenoalkanes
A subsection of Chemistry, 9701, through 15. Halogen compounds
Listing 10 of 284 questions
Hydroxyethanal, HOCH2CHO, has been observed in dust clouds near the centre of our galaxy. hydroxyethanal C HO C O H H H Predict the bond angles labelled x and y in the diagram of hydroxyethanal. C HO C O H H H x y  x = °  y = °  Hydroxyethanal reacts separately with 2,4-dinitrophenylhydrazine (2,4-DNPH) and with Tollens’ reagent. State what you would observe in each reaction. reaction with 2,4-DNPH reaction with Tollens’ reagent  Hydroxyethanal is converted to ethanedioic acid, (CO2H)2, when it reacts with excess acidified dichromate(ions, Cr2O7 2–. State the role of acidified Cr2O7 2– in this reaction. State and explain any other necessary conditions for this reaction to be successful. Hydroxyethanal can be reduced to ethane-1,2-diol, (CH2OH)2, as shown. hydroxyethanal C HO C O H H H ethane-1,2-diol C HO C OH H H H H Write an equation for the reduction of hydroxyethanal to (CH2OH)2. Use to represent an atom of hydrogen from the reducing agent. Identify a reagent for this reduction reaction. (CH2OH)2 also forms when an alkeneA reacts with cold, dilute, acidified manganate(ions. Name A. 
9701_m21_qp_22
THEORY
2021
Paper 2, Variant 2
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shows some reactions of compound D, 2‑bromobutane. D E Br H CH2NH2 G CN F OH reaction 2 AgNO3in ethanol reaction 4 KCN dissolved in ethanol reaction 1 addition polymer reaction 3 alkaline I2reaction 5 LiAlH4 yellow precipitate + an organic ion State the reagent and conditions used to form E in reaction 1. Draw the structure of one repeat unit of the addition polymer that forms from E. E also forms when F is heated strongly in the presence of an Al 2O3 catalyst. Write an equation for this reaction. Predict what is observed in reaction 2. Identify the yellow precipitate and the organic ion formed in reaction 3. yellow precipitate organic ion State the type of reaction that occurs in reaction 4. Reaction 5 is similar to the reaction of LiAl H4 with carboxylic acids to form alcohols. Suggest the role of LiAl H4 in reaction 5. shows the infrared spectrum of one of the compounds D, E, F, G or H. wavenumber / cm–1 transmittance / % Use information from Table 4.1 (on page 14) to identify which of the compounds D, E, F, G or H produces the infrared spectrum in . Explain your answer. Table 4.1 bond functional groups containing the bond characteristic infrared absorption range (in wavenumbers) / cm–1 C–O hydroxy, ester 1040–1300 C=C aromatic compound, alkene 1500–1680 C=O amide carbonyl, carboxyl ester 1640–1690 1670–1740 1710–1750 C≡N nitrile 2200–2250 C–H alkane 2850–2950 N–H amine, amide 3300–3500 O–H carboxyl hydroxy 2500–3000 3200–3600 In the mass spectrum of D, the relative abundance of the molecular ion peak is 3.4. Predict the relative abundance of the M+2 peak for D. Explain your answer.
9701_m23_qp_22
THEORY
2023
Paper 2, Variant 2
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