## 3 Discussion
The electron cloud of OH bond in the water was toward to the O atom originally and then moved to the side of the H atom. The electron cloud density deviates from the center of the two atoms, resulting in the reduction of vibration force constant and the increase of vibration frequency. Hence, the red-shift occurred in the OH bond. As so, the electrons in H were attracted to the oxygen side of the acetone, the O atoms in the water moved toward the side of H because of the H atoms to be attracted by hydrogen bonding, so that the OH bond length is reduced to achieve the electron density balance. In order to explore the hydrogen bonding between two kinds of molecules, the Raman shifts of C=O bond and OH bond with the variation of molar ratio were introduced, as shown in Figures 4 and 5. The Raman shift of C=O bond in different molar ratio acetone aqueous solutions were shown in Figure 4. With the increasing content of water, the characteristic peak of C=O stretching bond shifts towards the low wavenumber gradually and the maximum shift was about 11 cm\({}^{-1}\). However, the Raman shifts of the OH stretching bond moved to a high wavenumber with the acetone addition in the solutions, reaching the maximum shifts, 88 cm\({}^{-1}\), as shown in Figure 5. Compared to Figures 4 and 5, the blue shift of the OH bond is more significant than the C=O bond. The Raman shift of OH bond is about 8 times of C=O, which indicating that there are great influence on the water structure with the addition of acetone. It is resulted in the overall structure of water in the solutions and the average number of hydrogen bonds in the bulk water reduced. We have found from the hydrogen bond study of Tetrahydrofuran-water mixture that with the addition of water [43], the C-H bond length decreases gradually and shows a concentration dependence in the Raman spectrum. It should be noted that there existed similar changes in the acetone water binary solution system. With the increase of acetone in the binary solution, the combination of acetone and water molecules converted from single acetone molecule which acted on multiple water molecules, to single acetone molecule with the combination of single water molecule. The C=O bond length decreases as the concentration increases, and the frequency amplitude decreases in the Raman shift. Figure 3: Raman spectra for OH stretching bond of water and acetone aqueous solutions with different moral ratios (nCH\({}_{3}\)COCH\({}_{3}\):nH\({}_{2}\)O). a to o respectively correspond to pure water, 1:20, 1:10, 1:5, 1:4, 1:3, 1:2, 1:1, 3:2, 3:1, 5:1, 9:1, 10:1, 20:1 and pure acetone as a comparison. There showed more advantages for acetone molecules obtained water molecules from the tetrahedral hydrogen-bonded structure than the water molecules in the process of hydrogen bonds formed in the solutions with the hydrogen bonds been produced. The stable tetrahedral hydrogen-bonded network structure in the bulk water was broken so that some water molecules were forced to detach from the network. The water molecules formed a strong hydrogen bond with acetone, and increased the content of partially hydrogen-bonded water in the bulk water. It led to drop the surface tension rapidly in the water-rich region, as shown in Figure 1. As shown in Figure 4, as the content of water increased, red-shifts of the C=O bond in acetone exhibited, and the Raman shift rate gradually increased with the change of molar ratio, from a high molar ratio to a low because of the hydrogen bonding interaction between acetone and water. The hydrogen bonds increased with the increasing water. It can be seen from Figures 4 and 5 that the Raman shifts of the OH bond and the C=O bond has a similar tendency with the change of molar ratio. In the water-rich region, the two characteristic peaks moved fast towards high wavenumber and possess a large amplitude, so did not in the acetone-rich zone. This is because the hydrogen bonding in the mixed solutions is strengthened with addition of acetone, and it changed the interaction between molecules in the solutions.