Question 21M.2.sl.TZ2.4
| Date | May 2021 | Marks available | [Maximum mark: 14] | Reference code | 21M.2.sl.TZ2.4 |
| Level | sl | Paper | 2 | Time zone | TZ2 |
| Command term | Apply, Deduce, Determine, Draw, Identify, State | Question number | 4 | Adapted from | N/A |
Organic chemistry can be used to synthesize a variety of products.
Several compounds can be synthesized from but-2-ene. Draw the structure of the final product for each of the following chemical reactions.
[2]
Penalize missing hydrogens in displayed structural formulas once only.
Accept condensed structural formulas: CH3CH(OH)CH2CH3 / CH3CH2CH2CH3 or skeletal structures.
Determine the change in enthalpy, ΔH, for the combustion of but-2-ene, using section 11 of the data booklet.
CH3CH=CHCH3 (g) + 6O2 (g) → 4CO2 (g) + 4H2O (g)
[3]
Bonds broken:
2(C–C) + 1(C=C) + 8(C–H) + 6O=O / 2(346) + 1(614) + 8(414) + 6(498) / 7606 «kJ» ✓
Bonds formed:
8(C=O) + 8(O–H) / 8(804) + 8(463) / 10 136 «kJ» ✓
Enthalpy change:
«Bonds broken – Bonds formed = 7606 kJ – 10 136 kJ =» –2530 «kJ» ✓
Award [2 max] for «+» 2530 «kJ».
Award [3] for correct final answer.
Write the equation and name the organic product when ethanol reacts with methanoic acid.
[2]
Equation:
CH3CH2OH + HCOOH HCOOCH2CH3 + H2O ✓
Product name:
ethyl methanoate ✓
Accept equation without equilibrium arrows.
Accept equation with molecular formulas (C2H6O + CH2O2 C3H6O2 + H2O) only if product name is correct.
Oxidation of ethanol with potassium dichromate, K2Cr2O7, can form two different organic products. Determine the names of the organic products and the methods used to isolate them.
[2]
ethanal AND distillation ✓
ethanoic acid AND reflux «followed by distillation» ✓
Award [1 max] for both products OR both methods.
Combustion analysis of an unknown organic compound indicated that it contained only carbon, hydrogen and oxygen.
Deduce two features of this molecule that can be obtained from the mass spectrum. Use section 28 of the data booklet.
NIST Mass Spectrometry Data Center Collection © 2014 copyright by the U.S. Secretary of Commerce
on behalf of the United States of America. All rights reserved.
[2]
m/z 58:
molar/«relative» molecular mass/weight/Mr «is 58 g mol−1/58» ✓
m/z 43:
«loses» methyl/CH3 «fragment»
OR
COCH3+ «fragment» ✓
Do not penalize missing charge on the fragments.
Accept molecular ion «peak»/ CH3COCH3+/C3H6O+.
Accept any C2H3O+ fragment/ CH3CH2CH2+/C3H7+.
Identify the bond responsible for the absorption at A in the infrared spectrum. Use section 26 of the data booklet.
NIST Mass Spectrometry Data Center Collection © 2014 copyright by the U.S. Secretary of Commerce
on behalf of the United States of America. All rights reserved.
[1]
C=O ✓
Accept carbonyl/C=C.
Deduce the identity of the unknown compound using the previous information, the 1H NMR spectrum and section 27 of the data booklet.
SDBS, National Institute of Advanced Industrial Science and Technology (AIST).
[2]
Information deduced from 1H NMR:
«one signal indicates» one hydrogen environment/symmetrical structure
OR
«chemical shift of 2.2 indicates» H on C next to carbonyl ✓
Compound:
propanone/CH3COCH3 ✓
Accept “one type of hydrogen”.
Accept 
.