Zadanie 3b, Paper 2, listopad 2025, TZ1, Chemia IB HL
Wzorowane na: Chemistry HL Paper 2, November 2025, TZ1, pytanie 3(b). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Zadanie
Wspólne informacje do wiązki zadań
Many esters are still known by trivial names. Propyl ethanoate, CH3COOCH2CH2CH3, which has the odour of pears, is manufactured from propan-1-ol and ethanoic acid in the presence of an acid catalyst.
CH3CH2CH2OH(l) + CH3COOH(l) ⇌ CH3COOCH2CH2CH3(l) + H2O(l)
Both reactants can be synthesized from alkanes: propan-1-ol from propane via 1-bromopropane, and ethanoic acid from ethane via bromoethane and ethanol. The overall equation for the synthesis of the ester from the two alkanes is
Polecenie
(i) Oil of vitriol, spirit of hartshorn and wood alcohol are old trivial names still occasionally used for chemical substances, and names like these can be a source of confusion in international scientific communication. Outline how the modern system of naming compounds avoids this problem.
(ii) Shown below is the molecule of oil of wintergreen (methyl 2-hydroxybenzoate).
PowiększBesides its ester group, two further functional groups are present in this molecule. State their names.
(iii) Propyl ethanoate has the molecular formula C5H10O2. Deduce the structure and name of one of its functional group isomers.
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Pokaż rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) «IUPAC» systematic nomenclature / a single set of naming rules agreed internationally «by IUPAC» ✔
the name is derived from the structure «longest chain, functional group, positions of substituents» so that one name corresponds to exactly one structure ✔
(ii) hydroxyl «group» ✔
phenyl «ring» ✔
(iii) structure of a carboxylic acid with the formula C5H10O2, e.g. CH3CH2CH2CH2COOH drawn as a full or skeletal structure ✔
pentanoic acid ✔
Schemat punktowania
(i) M1: IUPAC / systematic international nomenclature; M2: names follow rules based on the structure of the molecule. (ii) [1] for each group; do not accept phenol, benzene ring or aromatic ring for phenyl, do not accept alcohol for hydroxyl, do not accept carbonyl (it is part of the ester). (iii) M1: structure of any non-ester isomer of C5H10O2 (a molecular formula alone is not accepted); M2: a name consistent with the structure drawn. Accept 2-methylbutanoic acid, 3-methylbutanoic acid, 2,2-dimethylpropanoic acid or any other correct non-ester isomer.
Komentarz. The OH on the ring is a phenol, but the IB name of the group is hydroxyl; a hydroxy-ketone or hydroxy-aldehyde with the formula C5H10O2 is also a valid functional group isomer.