Zadanie 5d
Wzorowane na: Chemistry HL Paper 2, November 2024, pytanie 5(d). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Informacja do zadań 5d-5g.
3-Methylbutanoic acid, (CH3)2CHCH2COOH, is responsible for the smell of some mature cheeses. Its molar mass is 102.15 g mol−1.
Polecenie
(i) Predict the number of signals in the 1H NMR spectrum of 3-methylbutanoic acid and the ratio of their areas.
(ii) Predict the splitting pattern of the signal due to the two hydrogen atoms of the CH2 group.
(iii) State one reason why tetramethylsilane, TMS, is a suitable reference standard in 1H NMR spectroscopy.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) number of signals: 4 ✔
ratio of areas: 6:1:2:1 «in any order» ✔
(ii) doublet ✔
(iii) any one of:
all 12 hydrogen atoms are in the same environment, giving one strong signal ✔
singlet / no splitting of the signal ✔
signal lies outside the range of the common chemical shifts ✔
volatile / easily removed after the measurement ✔
inert / stable ✔
Schemat punktowania
(i) M1: number of signals; M2: ratio, accepted in any order. (ii) [1]; accept "2" «peaks». (iii) [1] for any one reason. Stating that TMS has a chemical shift of 0 is not accepted as a reason.