EXAM 4 Flashcards
Label the indicated pairs of atoms or groups as Homotopic, Enantiotopic, or Diastereotopic.
Label the indicated pairs of atoms or groups as Homotopic, Enantiotopic, or Diastereotopic.
Label the indicated pairs of atoms or groups as Homotopic, Enantiotopic, or Diastereotopic.
Label the indicated pairs of atoms or groups as Homotopic, Enantiotopic, or Diastereotopic.
A compound shows sharp IR adsorption signals at 3300 cm-1 2200 cm-1. What functional group accounts for these adsorptions?
Terminal Alkyne
After working up the reaction, the student only obtained a 13C NMR. The following peaks appeared on the spectrum: 198.4, 154.3, 124.3, 31.6, 27.6, 20.6 ppm. Did the reaction work? Justify by assigning peaks to the correct carbons.
No, the reaction did not work. The 13C peaks at 154.3 and 124.3 ppm correspond to either aromatic or C=C carbons. The b-hydroxy ketone does not have aromatic or C=C carbons. The product would be expected to have 4 peaks deshielded to the chloroform solvent peak.
Draw the 1H NMR spectrum expected for the following compound using the scale below.
Clearly label the protons on the structure a, b, c, d,…. Label your spectrum showing which protons correspond to each signal, how many protons each signal represents (integration), and the multiplicity (splitting) of each signal.
Draw the 13C NMR spectrum expected for the following compound using the scale below.
Clearly label the carbons on the structure 1,2,3,4,… and label your spectrum showing which carbons correspond to each signal.
The molecular formula for an unknown material I as determined by mass spectrometry is C6H10O. Calculate the number of Double Bond Equivalents (unsaturation number). Show your work.
DBE = (2*6+2-10)/2 = 2
The molecular formula for an unknown material I as determined by mass spectrometry is C6H10O. From the IR spectrum for unknown I below, list frequencies and the functional groups present.
The molecular formula for an unknown material I as determined by mass spectrometry is C6H10O. IR showed functional groups including:
sp2 C-H stretch – left of 3000 cm-1
sp3 C-H stretch – right of 3000 cm-1
carbonyl stretch – 1695 cm-1
C=C stretch – 1605 cm-1
NO O-H, N-H, triple bonds, aromatic overtones
Identify the most likely structure for compound I.
A. The high resolution mass spectrum of an unknown compound II shows molecular ions at 185.9793 ([M], 100.0%), 186.9826 ([M+1], 6.78%), 187.9772 ([M+2], 97.3%), and 188.9806 ([M+3], 6.3%). Find the molecular formula for unknown II, but DO NOT try to identify the structure.
C6H7BrN2
Label the indicated pairs of atoms or groups as Homotopic, Enantiotopic, or Diastereotopic.
Label the indicated pairs of atoms or groups as Homotopic, Enantiotopic, or Diastereotopic.
Label the indicated pairs of atoms or groups as Homotopic, Enantiotopic, or Diastereotopic.
Label the indicated pairs of atoms or groups as Homotopic, Enantiotopic, or Diastereotopic.
The carbonyl stretching frequency of 2-cyclohexenone and 2-pentanone are very different. The frequencies are as follows: 1680 and 1720 cm-1. Please identify the carbonyl stretching frequency of each, and give a brief explanation to support your answer.
An undergraduate student attempted the following reduction. After working up the reaction, the student only obtained a 13C NMR. The following peaks appeared on the spectrum: 197.7, 144.0, 132.3, 27.5, and 19.0 ppm. Did the reaction work? Justify by assigning peaks to the correct carbons.
The reaction did NOT work because the peak at 197.7 ppm corresponds to a ketone. The product does not have a ketone.
Draw a coupling tree to illustrate how a “doublet of triplets” 1H NMR signal would appear if JHaHx = 8 and JHaHy = 4. Be sure to account for signal intensities.
The molecular formula for an unknown material I as determined by mass spectrometry is C7H9NO. From the IR spectrum for unknown I below, list frequencies and the functional groups present. Solve the structure.
primary amine (3500 cm-1, 3400 cm-1) sp3 C-H (3000-2800 cm-1) sp2 C-H (3100-3000 cm-1) aromatic overtones benzene (1600 cm-1 and 1500 cm-1) C-O stretches in fingerprint OOP bending (725 cm-1)
The high resolution mass spectrum of an unknown compound II shows molecular ions at 185.0244 ([M], 100%), 186.0277 ([M+1], 8.6%), 187.0214 ([M+2], 31.9%), and 188.0248 ([M+3], 2.8%). Find the molecular formula for unknown II, but DO NOT try to identify the structure.
C8H8NO2Cl
Which compound correlates to the following IR spectra?
Which compound correlates to the following IR spectra?
Which compound correlates to the following IR spectra?
Which compound correlates to the following IR spectra?
Which compound correlates to the following IR spectra?
The low resolution mass spectrum of an unknown compound A shows a molecular ion at 128 ([M], 100.0%). Use the “Rule of 13” to propose 3 reasonable molecular formulas for unknown compound A. For full credit, you must prove the molecular formulas are reasonable by calculating the degree of unsaturation (double bond equivalents) for each formula.
The high resolution mass spectrum of an unknown compound B shows molecular ions at 185.0607 ([M], 100.0%), 186.0641 ([M+1], 9.8%), and 187.0578 ([M+2], 32.1%). Find the molecular formula for unknown B, but DO NOT try to identify the structure. Please show all your work.
Label the indicated pairs of atoms or groups as Homotopic, Enantiotopic or Diastereotopic.
Diastereotopic
Label the indicated pairs of atoms or groups as Homotopic, Enantiotopic or Diastereotopic.
Enantiotopic
Label the indicated pairs of atoms or groups as Homotopic, Enantiotopic or Diastereotopic.
Enantiotopic
Label the indicated pairs of atoms or groups as Homotopic, Enantiotopic or Diastereotopic.
Homotopic
What is the unsaturation or double bond equivalent (DBE) formula and what does it help us calculate?
DBE= 2C + 2 - H - x + N/2
Helps calculate the number of pi bonds or rings in a molecule which helps solve for structure (will be important in spectroscopy
