Study On The Hydrogen Bonding Interaction In CHF₂CH₂NH₂-HX Complexes（X=NH₂,OH,F）

2,2-Difluoroethylamine（CHF₂CH₂NH₂）is an important aliphatic fluorine-containing compound,which is widely used the raw material or intermediate for the synthesis of many pharmaceuticals and pesticide products,exhibiting great industrial value.There are many preparation methods,and especially synthesis routes with ammonia are the most widely used.Among them,the reaction route of 1-chlorine-2,2-difluoroethane with excessive ammonia shows great industrialization potential due to its advantages of high conversion rate,high yield and short reaction time.However,due to the H atom on-NH₂group which shows strong activity,it is very easy to associate with ammonia through hydrogen bond（HB）,leading to the existence of NH₃-CHF₂CH₂NH₂complex in this system.However,few investigations concern this significant interaction that may cause great energy waste.In this study,the technical problems urgently need to be solved were studied combined with H₂O and HF from an aspect of Periodic Table of the Elements（in the same period with ammonia）,and the following results were achieved:（1）In this paper,1-chlorine-2,2-difluoroethane and excessive ammonia were adopted as raw materials to prepare 2,2-difluoroethylamine.The optimized process conditions were obtained by designing single factor experiment:Reaction temperature is 160℃,the pressure is 4 MPa,concentration ratio n（CHF₂CH₂Cl）:n（NH₃）is 1:3,reaction time is 9 h.Under these conditions,the product conversion rate was 93.51%,of which the conversion rate is high enough and the product selectivity is good with reaction time shortened.Finally,2,2-difluoroethylamine with a high purity of 99.8%（GC）was successfully prepared through fractionation.（2）The liquid hydrogen-bonding system involving 2,2-difluoroethylamine and ammonia or water（respectively）were acquired,and based on which NMR spectrum,FITR spectrum,surface tension detection and analysis were carried out.As a result,the chemical shift of NH₂group in the NMR spectrum shows a significant change.In the FTIR spectrum,the increasing intensity,widened shape and red shift of the vibration absorption peak confirm the existence of hydrogen bond interaction in this system.In addition,the surface tension enhances with ammonia and water mixing up with pure 2,2-difluoroethylamine in different ratios,which provides a reliable basis for the hydrogen bonding effect.Therefore,both NH₃and H₂O are prone to generate hydrogen bond interaction with 2,2-difluoroethylamine,exerting harmful effects on according technical processes.By using molclus and Gaussian software,high-level theoretical chemical calculations were performed rigorously.Seventeen configurations were picked up and charge transfer,electrostatic potential（ESP）and orbital analysis were carried out,and simultaneously,RDG and AIM topological plots were drawn to visualize the H-bond interaction.All configurations exhibit strong stability,where N-1a,O-1a and F-1a can be confirmed as structures with greatest stability in each system.According to electronegativity difference,HF and H₂O are found incline to form hydrogen bonds as proton donors,and on the contrary,NH₃tends to act as the hydrogen bond acceptor.（3）Based on AIM analysis,generalized equation applicable to estimate the hydrogen bonding strength between NH₂-containing molecules and HX（X=NH₂,OH,F）was obtained:Y=-0.0785X（10）0.1880（R²=0.947）Where,X is H···Y distance,and Y refers to the corresponding electron density.This proves that the hydrogen bond distance can be used as a good indicator of H-bond type and strength.Further,the interaction in CHF₂CH₂NH₂-HX system was studied firstly here in this study,and the results have significant reference value for similar analysis of H-bonds.（5）Boltzmann distribution analysis investigated implies that the temperature plays an important role in determining the distribution of stable conformation in CHF₂CH₂NH₂-NH₃system.Therefore,appropriate temperatures can be selected to low the proportion of stable conformation and thus reduce the subsequent separation energy consumption,which contributes to the national sustainable development strategy.