HW 5

pdf

School

Georgia Institute Of Technology *

*We aren’t endorsed by this school

Course

1315

Subject

Chemistry

Date

Dec 6, 2023

Type

pdf

Pages

Uploaded by HighnessStraw20983

HW #5, page 1 of 4 CHEM 1315 – Homework Set #5 (20 points) Due: 3:30 pm, Thursday, Nov. 16 th , 2023 Reading for this homework set: Klein volume 2, chapters 2 and 3, class notes lectures 19, 20 & 21. Key concepts: Light-matter interactions, UV-Vis Spectroscopy, Combustion Analysis, IR Spectroscopy, Mass Spectrometry, NMR Spectroscopy Please read the following instructions before proceeding:  Answers must be written inside the spaces provided or else they may not be found by Gradescope’s software. Anything written far outside the spaces will not be graded.  Upload this entire document in the correct order to Gradescope or else the software will have trouble organizing the pages properly.  You can reach Gradescope through the Canvas page.  Submit your answers as a PDF. 1. (3 pts) How many signals would you expect to see in the 1 H & 13 C NMR spectra of each compound below, (i.e. how many chemically distinct H & C atoms are present in each molecule?) (.5 pt each) # H signals: ___ ____ ____ # C signals: ___ ____ ____ Name:

HW #5, page 2 of 4 2. (2 pts) Combustion analysis on a molecule yields the following data: 54.53 wt% C, 9.15 wt% H, and 36.32 wt% O. Mass spectrometry data shows the M•+ peak has an m/z of 88. What is the chemical formula of the molecule? Show your work. 3. (3 points) Below are pairs of molecules. You are given a sample that contains one of them, but you don’t know which. Using FTIR, describe a spectral feature, or combination of features, that can be used to unambiguously identify which of the two compounds is the sample (note: be specific – e.g. do not say “I’d expect the spectrum to have a C=O peak if it’s the molecule on the right”; also list the approximate cm -1 where you’d expect to find this peak) (1.5 pts each): a) b)

HW #5, page 3 of 4 4. (3 points) Below are pairs of molecules. You are given a sample that contains one of them, but you don’t know which. Using 1H NMR or 13C NMR, describe a spectral feature, or combination of features, that can be used to unambiguously identify which of the two compounds is the sample (note: be specific – e.g. do not say “the splitting pattern is different”; quantify how many peaks or approximate ppm you’d expect) (1.5 pts each) : a) b) 5. A dye molecule is dissolved in a solvent, placed in a cuvette, and its UV-vis spectrum is shown at right. a) (1 pt) What energy of light in eV is being absorbed at 610 nm? Show your work. b) (1 pt) Given the molar absorptivity of the molecule is 122,000 M -1 cm -1 and the cuvette is 1 cm wide, what is the concentration of your sample? Show your work. a) b)

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

HW #5, page 4 of 4 6. (7 points) A molecule has the formula: C 9 H 10 O 2 . Using the spectra below, answer the following: a) Calculate the degrees of unsaturation: ____ (1 pt) b) How many non-equivalent carbons are there? ____ (1 pt) c) In the 1 H NMR spectrum, what structural motif gives rise to peak a ? (write the name or draw the motif) _______ (1 pts) d) In the 13 C NMR spectrum, circle the peak that corresponds to the structural motif identified above in part c) (1 pt) e) In the FTIR spectrum, circle two peaks > 1500 cm -1 that correspond to the structural motif identified above in part c) (1 pt) f) In the 1 H NMR spectrum, how many neighboring H’s does peak d have? ______ (1 pt) g) Draw the molecule (1 pts)