CHEM 237 Final Exam TAMU Everything (This QL includes every assignment from this class: sapling, discussion questions, the book, and important results from experiments) with Expert Verified Solutions

CHEM 237 Final Exam TAMU Everything (This QL includes every assignment from this class: sapling, discussion questions, the book, and important results from experiments) with Expert Verified Solutions Exp: Molecular Modeling - newman projection: staggered - newman projection: eclipsed - Newman Projection Conformations and their relative energies [draw a graph] - The gauche conformation of butane occurs when the dihedral angle between at the C1-C2 and C3-C4 is 60 degrees. There is sterric strain in the molecule due the proximity of the two methyl groups. Would the sterric strain in this molecule increase OR decrease C1-C2-C3 [and C2-C3-24] bond angle was increased to more than 109.5 degrees? - the sterric strain would decrease because the groups are moving farther apart The gauche conformation of butane occurs when the dihedral angle between at the C1-C2 and C3-C4 is 60 degrees. There is sterric strain in the molecule due the proximity of the two methyl groups. When you consider... E(strain) = E(strain) + E(angle) + E(torsion) + E(sterric) Would E(torsion) increase OR decrease when the dihedral angle of gauche butane was increased from 60 to 65 degrees? - E(torsion) increases [torsional strain] (The gauche conformation of butane occurs when the dihedral angle between at the C1-C2 and C3-C4 is 60 degrees. There is sterric strain in the molecule due the proximity of the two methyl groups.) Would the magnitude of this sterric strain increase OR decrease if the dihedral angle was increased from 60 to 65 degrees? Why? - the magnitude of the sterric strain will decrease because the groups are moving farther apart Identify the atoms that participate in the 1,3-diaxial interactions of cis-1,2-dimethylcyclohexane. How many 1,3-diaxial interactions are present in the molecule? - two exp: infrared spectroscopy - for an IR spectrum: what type of electromagnetic radiation is associated with the peaks in this column? - infrared radiation For an IR spectrum: what is the measured spectroscopic method? - the vibral frequency of the bond Infrared spectra are recorded using an ATR detector. What does ATR stand for? - Attenuated total reflectance Give two ways that infrared spectrophotometer fitted with an ATR sample IS advantageous over beamthrough-sample spectrophotometer? - 1. ATR allows for use of very small samples 2. sample preparation and clean up of an ATR is simple 3. Do beam-through-sample techniques... 1. have problems with nonpolar solvents? 2. require very expensive ZnSe sample holders? exaplain - 1. No - they can do polar/nonpolar equally 2. No - ATRs require the expensive ZnSe crystals What region if the IR spectrum is best used for distinguishing between isomers that have the same functional groups? - 1400-400 cm-1 The IR spectrum displays the wavelengths at which specific functional groups absorb energy. Which wavelength do each of these bonds absorb energy? 1. C--C [alkene] 2. C--O [ester] 3. O-H [carboxylic acid] - 1. C--C: 1600 cm-1 2. C--O: cm-1 3. O-H: cm-1 The IR spectrum displays the wavelengths at which specific functional groups absorb energy. Which wavelength do each of these bonds absorb energy? 1. C--C [Alkene] 2. N-H [amine] 3. C--O [ketone] - 1. C--C: 1600 cm-