FT IR & MS Spectra Acid Titration Curve & Molecular Structures Lab Report

 

This assignment requires the Lab Assignment 9 Data document (separate document on D2L).

Lab Assignment 9 concerns the analysis of FT-IR and MS spectra and weak acid titration curves to infer the molecular structure of organic weak acids. You can assume all the compounds are composed of only carbon, hydrogen and oxygen – and no other elements. In your analysis keep in mind carbon forms four bonds, oxygen two, and hydrogen just one. Double bonds count as “two bonds.” For example, with H2C=O, oxygen has “two bonds”, carbon four (two to oxygen and one each to two hydrogens)

Problem 1 (8p). Using only the FT-IR and MS spectra and the weak acid titration curve of Unknown A determine the molecular structure of Unknown A. Clearly justify your structure using the available data. Your analysis must include the FT-IR, MS and titration data. To receive credit, you must respond with well written, very legible, complete sentences that correctly employs chemical terminology and concepts.

Problem 2 (8p). Using only the FT-IR and MS spectra and the weak acid titration curve of Unknown B determine the molecular structure of Unknown B. Clearly justify your structure using the available data. Your analysis must include the FT-IR, MS and titration data. To receive credit, you must respond with well written, very legible, complete sentences that correctly employs chemical terminology and concepts.

Problem 3 (9p). Using only the FT-IR and MS spectra and weak acid titration curve of Unknown C determine the molecular structure of Unknown C. Clearly justify your structure using the available data. Your analysis must include the FT-IR, MS and titration data. To receive credit, you must respond with well written, very legible, complete sentences that correctly employs chemical terminology and concepts.

Lab Assignment 9 Data

The following data pertains to Lab Assignment 9 only – and is required to work the assignment.

UNKNOWN A

Unknown A, an organic weak acid composed of only carbon (C), hydrogen (H) and oxygen (O) gives the following weak acid titration curve, mass spectrum and FT-IR spectrum:

14

word image 716 word image 2010

12

10

8 pH

6

4

2

0

0 5 10 15 20 25 30 35 40 45 50

Volume of NaOH (mL)

 

Figure 1. Weak Acid Titration of Unknown A

word image 2011

Figure 2. Mass Spectrum of Unknown A

 

 

word image 2012 word image 717

Transmi

t

tance

 

 

(

cm

1

)

 

Figure 3. FT-IR Spectrum of Unknown A

UNKNOWN B

Unknown B, a different organic weak acid composed of only carbon, hydrogen and oxygen produces the following weak acid titration curve, mass spectrum and FT-IR spectrum:

word image 2013

0

5

1

0

1

5

0

2

3

0

3

5

0

4

25

2

4

0

6

10

12

14

8

p

H

Volume of NaOH (mL)

 

Figure 4. Weak Acid Titration of Unknown B

 

word image 2014

Figure 5. Mass Spectrum of Unknown B

(cm-1) Figure 6. FT-IR Spectrum of Unknown B

word image 718 word image 719

%

Transmi

t

tance

 

 

UNKNOWN C

Finally, Unknown C, yet another organic weak acid composed of only C, H and O, gives the following weak acid titration curve, and mass and FT-IR spectra:

14

word image 2015 word image 2016 word image 2017

12

10

8 pH

6

4

2

0

0 5 10 15 20 25 30

Volume of NaOH (mL)

 

Figure 7. Weak Acid Titration of Unknown C

word image 2018

Figure 8. Mass Spectrum of Unknown C

 

word image 720 word image 721

%

Transmi

t

tance

 

Figure 9. FT-IR Spectrum of Unknown C (cm-1)

 

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