Chem 236 Homework 2 1 Draw a Lewis structure for the following species Show all formal charges and lone pairs if applicable Then compute the oxidation number for each atom in the structure a NH3 Ne 4 H 1 N 3 H la F 10 B M H 1 N 3 B 3 F I FIF 111111 F H H H 0 For 1d dihydrogen cation draw an orbital interaction diagram Based on your analysis is the dihydrogen cation likely to exist as a diatomic species or would it dissociate into monoatomic fragments Explain t H2 H H Y TS IS Fis is more likely to exist as a diatomic cation The the MO with lower when the e is in the AO of a Hydrogen atom e is a bonding orbital because energy compared to b NH4 c BF4 d H2 Hz 2 a Draw the curved arrows to convert each resonance structure to the next left to right F L 8 b Which resonance structure contributes most to the resonance hybrid of this molecule Why brid hy The first structure shown contributes most to the resonance All atoms have a formal charge of 0 and follow the octet rule The stability ranking of the rest of the resonance structures 11 121 V 1 3 Draw reasonable resonance structures for each of the following species O O O O T a b O O Y T O E NH2 GNH2 NH2 4 CH3CH CH3 CH CH3 CH2CH2CH3 2 6 5 a What is the IUPAC name for the alkane shown 2 3 dimethylhexane b Relative to the bond between carbons 3 and 4 as labeled draw the six Newman projections corresponding to 60 rotations about this bond back carbon rotates Reminder isopropyl group can be abbreviated as iPr iPr iPr iPr iPr iPr iPr H H H CHICH3 H CHICHs H 4 CH2CH3 crisk crs acre ricrs acri 3CHICH3 CH2CH3 H CH2CH3 2 H 3 4 H 5 6 Lowest E c Indicate any unfavorable steric interactions below each conformer above label Highest E both the highest and lowest in energy Then draw a qualitative energy diagram for the rotation of this bond 2 4 6 as they can 1 No unfavorablestericinteractions Thelargegroups areas far apa TheconformerisintheeclipsedformThegroups n 3 5 StaggeredformbuttheC and isopropy groups areora 4 6M 2 5 3 so no iso 240 500 360 Angle of rotation Relative Energy 5 a Considering the reaction of phenol pKa 10 with sodium hydroxide pKa of water 14 above indicate which reactant acts as a Br nsted acid and which acts as a Br nsted base Then circle the side which is favored by equilibrium Acid Base OH phenol b Draw three resonance forms of phenoxide O L O O o c In the reaction of ethanol pKa 16 with sodium hydroxide circle the side which is favored by equilibrium How does your answer for 5b help justify any di cid 431 erences in reactivity between phenol and ethanol O The resonance structures indicates that molecule more polarized Thenegativechargetowardsitmakingaa a probability to pull more partially positive the ring in phenol and is more reactive when it encounters an anion the has Y OH