Table 1: Properties of the isolated CH3CHO and H2O molecules, A and B complexed with 1 and 2 water molecules (distances in Å , σ *occupation in e, hyperconjugation energies in kcal mol−1, and frequencies in cm−1).

Isolated CH3CHOA(1-1)A(1-2)B(1-1)B(1-2)

𝑟 ( C 1 H 3 ) 1.11221.10941.10941.10821.1054
𝜈 ( C 1 H 3 ) 28712905290629232964
𝜎 ( C 1 H 3 ) 0.0710.0640.0630.0620.057
% 𝑠 C 1 ( H 3 ) 30.030.029.730.031.7
𝑞 ( C 1 ) 0.4420.4630.4740.4570.451
𝑞 ( H 3 ) 0.0920.1030.1030.1160.153

𝑟 ( C 4 H 5 ) 1.08981.08971.09101.08961.0898
𝜈 ( C 4 H 5 ) 31363142312531393136
𝜎 ( C 4 H 5 ) 0.00660.00710.01220.00640.0065
% 𝑠 C 4 ( H 5 ) 25.426.227.0525.4625.48
𝑞 ( C 4 ) −0.679−0.689−0.699−0.679−0.680
𝑞 ( H 5 ) 0.2220.2450.2620.2240.222

𝑟 ( C 1 = O 2 ) 1.2061.2121.2141.2121.218
𝜈 ( C 1 = O 2 ) 18081789178317881764

L P O 2 𝜎 ( C 1 H 3 ) 23.6422.4322.2220.7118.84
L P O 1 2 𝜎 ( C 1 H 3 ) 2.70
L P O 2 𝜎 ( O 9 H 8 ) 7.119.937.359.34
L P O 9 ( O 1 2 ) 𝜎 ( C 4 H 5 ) 0.462.95

Isolated H2OA(1-1)A(1-2)B(1-1)B(1-2)

𝑟 (OH)0.96200.97110.9755a0.97110.9777a
0.9760b0.9764b
𝜈 (H2O)3926,38203894,36813889,3629c3894,36803888,3579c
3890,3579d3890,3603d
Σ 𝑞 (H2O)−0.017+0.009e−0.019−0.004e
−0.017f−0.017f

a O 9 H 8 bond. b O 1 2 H 1 1 bond. 𝑟 (OH) in the water dimer is 0.9700 Å. cν( H 8 O 9 H 1 0 ) dν( H 1 1 O 1 2 H 1 3 ), e Σ 𝑞 on ( H 8 O 9 H 1 0 ) f Σ 𝑞 on ( H 1 1 O 1 2 H 1 3 ).