方酸的性质特征和氮方酸、氮氧方酸及氮硫方酸的结构分析

PROPERTIES AND CHARACTERISTICS OF SQUARIC A CID AND STRNCTURE DETERMINATION OF NITROGEN SQUARIC ACID, NITROGEN OXOSQUARIC OXOSQUARIC A CID AND NITROGEN SURFOSQUARIC A CID

扩大和充实了方酸的定义，描述了方酸应有的共同特征，对氮方酸、氮氧方酸和氮硫方酸的结构作了表征．对方酸这类以芳香性方形四碳环为重要特征的、反应性能丰富的基本物质进行了研究．

n extensive definition of squaric acid is proposed. Acoording to the definition anycompounds which have following formula can be named after squaric acid:X=YorX≠Y.X,Y=OH,NH_2.SH. PH_2……The different combination of X and Y can form different types of viuaric acid. We can distinguishthem with different title. For example: X=Y=OH Oxosquaric acid X=Y=NH_2 Nitrogen squaric acid X=OH,Y=NH_2 Nitrogen oxosquaric acid X=SH Y = NH_2 Nitrogen sulfosquaric acid X=Y=SH Sulfosquaric acid X=Y=PH_2 Phosphorous squaric aicd X=OH Y =SH Sulfoxo squaric acid X=OH Y=PH_2 Phosphorous oxosquaric acid X=PH_2 Y=NH_2 Nitrogen phosphorous squaric acidand so on. It may be named after pseudosquaric acid when hath or either of the oxygen atoms at 1,2-position of the four carbon ring are substituted by orther atoms and function groups such as S,NH.Although the different types of squaric acid containe the different function groups at 3,4-position of four carbon ring,and exhibite the different reactivity and selectivity,there are manycommon characteristics:1.The a frame structure:There is a four carbon ring in the compounds. In fact,there is nocarbou-carbon double bond in the ring,double bond is just used as a way for describing structure ofthe ring.It is very similar to the way used by Kekule formula to describe the structure of benzene.The bond lengths of the four Carbon-Carbon bonds are 0.145±0.010nm. The values are shorterthan the typical single,but longer than the double bond.The four carbon ring is nearly square andthe length of two carbon-oxygen bonds at 1.2-position is0.12nm which is vevy near the bondlength of carbenyl c=0.2.The four carbon ring is a closed delocalized system of two electrons and is highly polarized.This system is satistied with Hukel 4n+2 rule(n=0)and exhibits pecial aromaticity. The fourcarbon atoms in the ring and other four heteroatoms such as N、P、O、S attached to the ring are in thesame plane. 3.Contrat to benzene ring structure with the rich charge,the four carbor ring is poor chargeand stable structural unit.The poor level of charge depends on the property and position of atoms orgroups attached to the ring. The behaviors of the whole ring resemble greatly mettallic ion in thechemical properties. In other words,the four carbon ring of derivetives of squaric acid exhibits thefunetion of“electronric trap”.4.The squaric acids desecribed above are low molecule weight and highly thermal stabilitymaterial. Their melting points are obscure and the solubilites in common organic solvent are vevylow. They are all dihasic acids.Sulphosquaric acid is the strongest acid and acidity of nitrogensquaric acid is very weak among squaric acids. 5.Whether the nucleophilic substitution reaction is occured in the four carbon ring or thetrasformation of the fundametal group attached to the ring is carried out,the resulting compoundsare the 1,3-(diagonal)or 1,2-(ortho)position products,the square structure of the four carbonring does not change which is similar to the effectt of substituted groups in benzene ring.The structural determinations of nitrogen squaric acid,nitrogen oxosquaric acid and nitrogensulfo squaric acid are carried out by elemental analysis,IR,UV/vis,1H、3) C NMR and MS. K