SolnsChap14EVENZum7e

The type of bond formed from the 2pz and 1s orbitals

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Unformatted text preview: rbitals with a 2s orbital from beryllium. Assuming the z axis is the internuclear axis in the linear BeH2 molecule, then the 2pz orbital from beryllium has proper symmetry to overlap with the 1s orbitals from hydrogen; the 2px and 2py orbitals are nonbonding orbitals since they don’t have proper symmetry necessary to overlap with 1s orbitals. The type of bond formed from the 2pz and 1s orbitals is a sigma bond since the orbitals overlap head to head. The MO diagram for BeH2 is: Be 2H !* s !* p 2px 2p #" 2s #" 2py # 1s # 1s !p #" !s Bond order = (4 - 0 )/2 = 2; the MO diagram predicts BeH2 to be a stable species and also predicts that BeH2 is diamagnetic. Note: The σs MO is a mixture of the two hydrogen 1s orbitals with the 2s orbital from beryllium, and the σp MO is a mixture of the two hydrogen 1s orbitals with the 2pz orbital from beryllium. The MOs are not localized between any two atoms; instead, they extend over the entire surface of the three atoms. CHAP. 14 597 COVALENT BONDING: ORBITALS - EVEN-NUMBER PROBLEMS 84. a. The NMR indicates that all hydrogens in this compound are equivalent. A possible structure for C2 H3Cl2 that explains the NMR data is: H C C H H Cl Cl Cl Note that for organic compounds to have a zero formal charge for all atoms, carbon will always satisfy the octet rule by having four bonds and no lone pairs, oxygen will always satisfy the octet rule by having two bonds and two lone pairs, and Cl will always satisfy the octet rule by having one bond and three lone pairs of electrons. b. We have two “types” of hydrogens. The triplet signal is produced by having two neighboring C−H bonds, whereas the quintet signal is produced by having four neighboring C−H bonds. A possible structure that explains the NMR (number of peaks, types of peaks, and the 2:1 relative intensities of the signals) is: H H C C C H Cl H H H Cl c. Data: Three “types” of hydrogens; the singlet peak is produced by having no neighboring C−H bonds, the quartet signal indicates three neighboring C−H bonds, and the triplet indicates two neighboring C−H bonds. A possible structure to explain the NMR is: Quartet sign al Trip let sign al H H H O C C C H H O H Singl et sign al CHAP. 14 598 COVALENT BONDING: ORBITALS - EVEN-NUMBER PROBLEMS d. Data: Three “types” of hydrogens. A possible structure to explain the NMR is: Doub let signal H H H O C C H C HH C C H H H Hept et sign al Sin glet sign al H e. Data: Three “types” of hydrogens. A possible structure to explain the NMR (number of peaks, types of peaks, and relative intensities) is: H O C C C H Trip let H sig nal H H H Trip let sig nal Quin tet sign al Note that the two hydrogens in the –CH2 group have four total neighboring protons (3 + 1), giving the quintet signal. The –CH2 g roup protons also cause the other “types” of hydrogens to have triplet signals. NEXT PAGE ….. MARATHON PROBLEM….. CHAP. 14 599 COVALENT BONDING: ORBITALS - EVEN-NUMBER PROBLEMS Marathon Problem 86. φ1, φ2, and φ3 all must be normalized. ∫φ12 dT = 1 = 4 A2 = 1 − 1 ∫φs2 dT + 4 A2∫φpx2 dT + 2 3 1 2 1 = , A2 = , A = 3 3 6 ∫φ22 dT = 1 = 1 6 12 1 ∫φs dT + A2∫φpx2 dT + B2∫φpy2 dT + 2 (−A) ∫φs φpx dT 3 3 +2 1= 1 1 2A ∫φs φpx dT = + 4(A2)(1) + 0 3 3 1 1 (B) ∫φs φpy dT − 2 AB∫φpx φpy dT = + A2 + B2 + 0 + 0 + 0 3 3 1 1 1 + + B2, = B2, B = 3 6 2 1 2...
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This note was uploaded on 01/26/2014 for the course CHEM 001 taught by Professor Giancoli during the Fall '12 term at UPenn.

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