Vibrational frequencies of water molecule

Vibrational frequencies of peeing moleculeQuestion 1 Normal modes and vibeal frequencies of piddle moleculeHF/3-21* optimised geometry of the water moleculeH coalition duration0.967HOH bond wobble107.7(ii) button of the HF/3-21G optimised water molecule = -75.58596 auCycle verveMax. Grad.Max. Dist.175.585530.012460.00304275.585890.003240.00025375.585960.000010.00000 relative frequency (cm-1)Relative Motion continue or Bend emblemSymmetry (S or A)1799.2BendA1S3812.2StretchA1S3945.8rStretchB1AHODEnergy75.58596 auGeometryBond angle107.7Bond length0.967Vibrational frequencies1578.7H moves double-quick than D symmetric2815.3D moves quickly whereas H moves slightly asymmetrical3881.7H moves quickly whereas D moves slightly asymmetric Normal modes and vibrational frequencies of the water dimmer (H2O)2Hydrogen-Bond AcceptorHydrogen bondHydrogen Bond sponsorHydrogen bond length (HO) = 1.808Hydrogen bond angle (O-HO) = 174.9Energy of the F/3.12G optimised water dimer = -151.18902 au (a) Potential energy calculationE = E(dimer) 2xE(H2O) = (-396 871.2KJ/mol) 2x(-198 413.2KJ/mol) = (-396 871.2) (-396 826.3) = 44.9 KJmol-1(b)As seen from the surface diagram for H2O, the group O has negative charge (-) whereas the hydrogens ar positively charged (+).In the water dimer molecule, the hydrogen atoms (on the H-bond donor group O) are +/ sulky region. The oxygen atom that is bonded to the hydrogen that is the H-bond acceptor has - charge/red region. Between in the H-bond, the positive(H) and negative(O) charges combine/green region.The hydrogen bond is make between superstar of the H atoms and hotshot O, instead between the ii oxygens, because the devil oxygen atoms are negatively charged, and have -, and then repulsive interactions are formed between them. So, virtuoso H reacts with the O, which donates one of its lone pairs to form the H-bond.In the structure of the molecule, the HO bond is al roughly linear, very close to one hundred eighty but it is di storted so it is about 175. Also, the distortion causes the bond HO to become longer.(c) For the water moleculeH bond length = 0.967For the water dimer H bond length of H-bond donor = 0.965 H bond length of H-bond acceptor = 0.966, 0.974 (H of H-bond)The H bond length of the hydrogen of the H-bond is bigger than the other O-H bonds in the molecule. This is because this H is bonded to the oxygen through the H-bond, and it is pulled towards the oxygen, causing its bond with the other oxygen to become a bit longer.Question 2The water dimer consists of 2 breaks, the H-bond acceptor (top OH2 group) and the H-bond donor (bottom OH2 group). When a vibration causes both fragments and H-bond to move, then it is considered to be the inter-monomer because it is a vibration between the two molecules. If only one of the fragments vibrates, then the vibration is only in one of the molecules (it is internal) and it is considered to be an intra-monomer.The vibrational frequencies of the water dim er are the followingFrequency = 81 cm-1 attribute = A crook elbow roomTop ploughshare of the molecule abject slightly up and elaborate, part the two bottom hydrogens move up and down as tumefy Inter-monomer The vibration affects both molecules connected through the hydrogen bond. Frequency = 133 fibre = A Bending mode Top part and bottom part moving right and left. Inter monomerFrequency = 172 suit = ABending mode Middle hydrogen moving right and left and two bottom H atoms moving up and down symmetrically (when one is up, other is down) Inter MonomerFrequency = 242Type = A stretchiness flair Inter monomer Frequency = 425Type = ABending direction The H-bond acceptor fragment moves to the front and then back, and the H-bond donor fragment moves up and down as well. Inter-monomer Frequency = 826Type = ABending modeThe H of the H-bond ( philia H) is moving to the right and left, causing the rest of the molecule to move in that personal manner as well Inter-monomer Frequency = 1782Type = A Bending Mode The hydrogen atoms on the H-bond donor fragment move up and down to the sides going further away and then coming close-set(prenominal). Intra-monomer Frequency = 1854Type = A Bending Mode The hydrogen atoms on the H-bond acceptor fragment develop and go further away and then come closer unitedly again. Intra-monomer Frequency = 3724Type = A Stretching mode The hydrogen forming the H-bond moves closer to the oxygen of the H-bond and then further from it, causing the O-H bond to come little and the HO bond to become bigger, and the opposite. Intra-monomer Frequency = 3849Type = A Stretching mode The hydrogen atoms move symmetrically so that their bonds with the O of the H-bond donor are becoming bigger (stretch out) and then smaller. Intra-monomer Frequency = 3907Type = A Stretching mode The O-H bond of the H not involved in the H-bond acceptor fragment is stretching out, causing the bond to become longer, while the bond of the oxygen with the other H, which is involved in the H-bond, becomes shorter. Intra-monomer Frequency = 3982Type = A Stretching mode It is an unsymmetrical movement, where one O-H bond in the H-bond donor fragment becomes shorter and the other longer. Intra-monomerQuestion 3Isotopic substitution in the water dimer Free Energy (H-TS) = 37.8 intact = 127.5 Free Energy (H-TS) = 39.7 Total = 126.5G = G(B) G(A) = 39.7KJmol-1 37.8KJmol-1 = 1.9 KJ/molK = e(-G/RT) = exp(-1.910-3Jmol-1/8.314JK-1mol-1x298K) = 1.00000077Deuterium prefers the position shown in B (connected to the oxygen of the H-bond acceptor fragment, but doesnt take part directly in the H-bond) because the molecule has higher free energy for this arrangement.Question 4Interconversion of water dimer structuresFrequency = i302Type = B1Frequency = 105Type = B2Frequency = 208Type = A1Frequency = 225Type = B1Frequency = 256Type = A2Frequency = 591Type = B2Frequency = 1785Type = A1Frequency = 1831Type = A1Frequency = 3829Type = A1Frequency = 3862Type = A1Frequency = 3952Type = B1Frequency = 3961Type = B2Acyclical water dimer cyclic water dimer The acyclic water molecule energy is 3.96910-5 KJmol-1 whereas the energy of the cyclic one is -. The cyclic molecule is less stable than the acyclic one because its ability to move around is effectively reduced compared to the acyclic one, callable to the two bonds formed between the oxygen of one molecule and the two H of the other molecule. The speculative frequency has the value of i306.9. One of the middle hydrogens moves up while the other moves down, in an unsymmetrical movement as shown in the pictures above. For the acyclic water dimer there are no fanciful frequencies and it corresponds to the valley. This shows that it is very stable and this structure is preferred.The cyclic molecule contains one vibrational frequency and this suggests that it is not as stable as the acyclic one. It corresponds to the supercilium of molecule- softwood.If a molecule has more than one vibratio nal frequency it corresponds to the mountain passes and it is a very runny and unfavoured structure for the molecule to be at, which most probably does not exist. The cyclic structure is not very stable, and therefore it is not preferred over the acyclic one.Question 5Syn-butaneNo imaginary frequencies Valley stable structure, highly favouredBoat cyclohexanene imaginary frequency Hilltop fairly unstable, exists but not preferredAll-syn cyclohexaneto a greater extent than one imaginary frequencies Mountain Pass does not exist, very unstable