Interpret the functional group region of an IR spectrum by matching absorption bands to bond types (O-H, C=O, C-H, N-H, C=C) with the wavenumber table in the data booklet, and use the spectrum to confirm or rule out functional groups.
Tę umiejętność sprawdza 27 zadań wzorowanych na arkuszach IB z lat 2022–2026.
Pentan-2-ol will react with acidified potassium dichromate, K2Cr2O7, which is an oxidizing agent. (i) State the name of the product of this reaction. (ii) Explain how infrared spectroscopy could be used to distinguish between pentan-2-ol and the product…
Compound X is a flavour compound that occurs in many plants. Its structure is shown below. (i) State the IUPAC name of compound X. (ii) State the name of the functional group represented by the C=O bond itself in compound X. (iii) Predict the size of the H–C=O…
A chemist wants to confirm that a sample of an unknown organic compound contains a carbonyl group, C=O. Which technique gives this information most directly? A. Mass spectrometry B. Paper chromatography C. 1H NMR spectroscopy D. Infrared…
(i) Determine the molecular formula and the empirical formula of cresolphthalein. (ii) A simplified infrared (IR) spectrum of cresolphthalein is shown below. State the bonds responsible for the absorptions labelled P, Q and R. Use section 20 of the data…
The mass spectrum of carbonyl dibromide is shown below. Bromine has two isotopes, and , of almost equal abundance. (i) Explain the origin of the peaks that appear at m/z values smaller than those of the molecular ion. (ii) Deduce…
What is a limitation of infrared (IR) spectroscopy in determining the structure of an organic compound? A. The sample is destroyed during the analysis B. Structural isomers containing the same functional groups give very similar spectra C. It cannot detect…
Below is the infrared spectrum recorded for ester Y. (i) This spectrum contains two peaks that confirm Y is an ester. Deduce their identity, giving the wavenumber and the bond responsible for each. Use section 20 of the data booklet. (ii) Alcohols and…
Iodoethane can react with aqueous hydroxide ions to produce ethanol. CH3CH2I(l) + OH−(aq) → CH3CH2OH(aq) + I−(aq) (i) State what type of reaction this is. (ii) Using curly arrows to show the movement of electron pairs, sketch the mechanism of this…
The IR spectrum of HA is shown. Two absorption bands are labelled: Y is a very broad band centred near 3000 cm−1 and Z is a band of medium intensity near 1650 cm−1. (i) Using section 20 of the data booklet, identify the functional…
(i) Draw the structural formula of 2-chloropentane and that of the structural isomer in which the chlorine atom is attached to a tertiary carbon atom. (ii) Only one of the two isomers drawn in (c)(i) is chiral. Draw stereochemical formulas showing its two…
Methane, carbon dioxide and water vapour are all greenhouse gases. Which property do these gases share that makes them greenhouse gases? A. They absorb the ultraviolet part of solar radiation before it reaches the Earth's surface. B. They are all produced only…
The infrared (IR) spectrum of A is given below. Identify the bond that gives rise to absorption B. Use section 20 of the data booklet.
The infrared (IR) spectrum of a sample of a polymer used in wood adhesives is shown. Deduce the bonds in the polymer that are responsible for peaks A and B. Use section 20 of the data booklet.
Identify one absorption range in the IR spectrum of propanoic acid that is not present in the IR spectrum of propan-1-ol. Use section 20 of the data booklet.
4-Phenylbutan-2-one is made by oxidizing 4-phenylbutan-2-ol. A sample of the product is contaminated with some unreacted alcohol. The infrared spectra of the pure ketone and of the pure alcohol are shown. Deduce, giving two reasons, which spectrum belongs to…
Predict one wavenumber at which an absorption, other than that of a C–H bond, appears in the infrared spectrum of 3-methylbutanoic acid. Use section 20 of the data booklet.
Ethyl 4-hydroxybenzoate is a preservative used in some oral medicines. It was synthesized by heating 0.745 g of 4-hydroxybenzoic acid with excess ethanol and a few drops of concentrated sulfuric acid as catalyst. C7H6O3 + C2H6O ⇌ C9H10O3 + H2O Mr…
An unknown organic compound, X, contains only carbon, hydrogen and oxygen. Elemental analysis shows that it contains 54.5 % carbon and 36.3 % oxygen by mass. (i) Determine the empirical formula of X. The mass spectrum of X is shown. (ii) Identify the species…
The skeletal formulae of two esters with the molecular formula C4H8O2 are shown. (i) Deduce the number of signals you would expect in the 1H NMR spectrum of each compound. (ii) Outline why infrared spectroscopy is not used to differentiate between…
Outline what happens to a molecule of methane, a greenhouse gas, when it absorbs infrared radiation.
Spectra can be used to monitor the conversion of ethanoic acid into the ester. (i) State one similarity and one difference between the infrared (IR) spectra of ethanoic acid and of the ester in the 1500–3500 cm−1 region. Use section 20 of the…
The conversion of propanoic acid into the ester can be followed by changes in spectra. (i) Compare the infrared (IR) spectra of propanoic acid and of the ester between 1500 and 3500 cm−1 by stating one feature they share and one feature in which…
Benzocaine, a local anaesthetic, is the ethyl ester of 4-aminobenzoic acid. The crude product of its synthesis is purified by recrystallization. (i) Discuss two ways in which the melting point of the recrystallized benzocaine can show that it still contains…
A tablet contains either aspirin or paracetamol as its active ingredient. The structures of the two compounds and the IR spectrum of the active ingredient are shown. Deduce whether the active ingredient is aspirin or paracetamol, and give two reasons that…
Benzocaine is a local anaesthetic. It is made by reacting the carboxylic acid X with ethanol. (i) Discuss two ways in which the melting point of a crystallized sample of benzocaine can show that it still contains X. (ii) Deduce the range of wavenumbers in the…
Menthol is a secondary alcohol used in cough lozenges. A chemist heated menthol with an oxidizing agent and isolated the product, which is either unreacted menthol or its oxidation product menthone. The structures of the two compounds and the IR spectrum of…
What information about pentan-2-one, CH3COCH2CH2CH3, can be obtained from mass spectrometry (MS), infrared (IR) spectroscopy and 1H NMR spectroscopy? A. MS: the compound contains a carbonyl group; IR: the molar mass is 86 g mol−1;…
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