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BIOC10001: Biomolecular Spectra and Mechanisms Assignment
2023-2024
Add your answers to the accompanying answer sheet including submitting images of any hand_x005f drawn structures and/or mechanisms. The answer sheet must be submitted via Blackboard (full
instructions on the Week 11 page of the BC1A Blackboard site) by 14:00 (2 pm) on Friday 5th
January 2024. Normal late penalties will apply.
All questions contribute equal marks. This assignment contributes 10% to the overall Unit mark.
n.b. A data sheet with characteristic spectral parameters can also be downloaded.
Question 1:
(a). The following IR spectrum represents one of the four listed compounds. Which is it Identify
the characteristic diagnostic peaks and briefly explain your reasoning. [30% ofmarks]
A- Acetic acid CH3COOH
B- Ethanol CH3CH2OH
C- Diethyl ether CH3CH2OCH2CH3
D- 3-pentanone CH3CH2C(=O)CH2CH3
(b). IR spectra for the other 3 compounds in the list above are shown on the following page. Match
each of these spectra to their compounds. Explain your reasoning and identify the signals
corresponding to the relevant functional groups. [60% of marks]
IR spectrum #2
IR spectrum #3
IR spectrum #4
(c). Now draw the chemical mechanism for the reaction of compound A with compound B, naming
the product formed. What pH conditions would favour this reaction [10% ofmarks]
Question 2:
(a) Explain how these isomers could be distinguished by mass spectroscopy. [50% of marks]
(b). Show the structures of positive ion fragments of 2-heptanone that account for mass spectrum
peaks of m/z=43 and m/z=99 respectively. [50% of marks]
Question 3:
A small organic compound was isolated from apple juice. It was found to have a molecular weight of
98 and comprised only C, H & O atoms. IR, 1H-NMR and 13C-NMR spectra of the compound were
collected and are shown below.
(a) Interpret the IR spectrum, explaining which peaks arise from which functional groups in the
compound. [30% of marks]
(b) Explain the chemical shift, integral and multiplicity of each peak in the 1H NMR spectrum and the
chemical shifts in the 13C NMR spectrum. [50% ofmarks]
(c) Combine all of these data to describe a possible structure for the compound. [20% of marks]
IR:
3 3
1
1
2
1H-NMR: n.b. the spectral peaks are annotated with the number of 1H atoms contributing to each
peak (i.e. the integration)
13C-NMR
Question 4:
A team of researchers isolate what they believe to be the compound shown below (Compound X) from the
bark of a rainforest tree. This compound is known to be responsible for the antibacterial properties of the
tree bark, which has been used for centuries by indigenous peoples in the treatment of infectious disease.
Compound X
(a) Draw a predicted 1H NMR spectrum for Compound X. You should include peak integration data in your
spectra. [70% of marks]
(b) The researchers collect a 13C NMR spectrum of the isolated compound. They are surprised to discover
that the spectrum lacks the expected peaks at 71.5 ppm, 20.6 ppm, and 16 ppm. Based on these findings
draw a revised structure of the isolated compound and describe how it differs from compound X. [30% of
marks]
Question 5:
For the following incomplete mechanism of an enzymatic reaction:
(i) Identify the substrate/product components (1), (2) & (3). [30% of marks]
(ii) Draw the structure of the modified form of the co-factor labelled (4). [20% ofmarks]
(iii) Add curly arrows to the overall diagram to show the flow of electrons throughout this
mechanism. (You can either add these to the figure or draw out the mechanism by hand
and add the arrows, then upload a picture of your diagram). [50% ofmarks]
Question 6:
Including the structure below, the following molecule can exist in three tautomeric forms.
a) Sketch the two additional tautomeric forms of this molecule. [10% ofmarks]
b) Draw the 1H spectra of all three tautomeric forms. [90% ofmarks]