duminică, 7 aprilie 2013

ACYCLIC HYDROCARBONS

ACICLYC HYDROCARBONS

 
DEFINITIONAlkyne are called unsaturated acyclic hydrocarbons containing in their molecule a triple bond. Between 2 at. C and the ratio and the ratio between no. of at. C and H is given by the formula CnH2n-2 where n = no. of at. R of the molecule.
Features: alkynes are: hydrocarbons

                                         -acyclic
                                         -unsaturated
( NE = 2, due presents leg.π in connection component. Triple )
Nomenclature. Homologous series.
            Giving obtain integer values ​​of n homologous series in which the terms in any homologous series, 2 consecutive terms is differentiates between them by a methyl group. (-CH2-)

   Name alkynes are formed by replacing suf - year of the corresponding alkane with suf​​-ina. Homologous series starts at n = 2


n
CnH2n-2
Alcan
CnH2n-2
Alchina
1
CH4
Metan
-
-
2
C2H6
Etan
C2H2
Etina (acetilena)
3
C3H8
Propan
C3H4
Propina
4
C4H10
butan
C4H6
butina
 
 Alkyne radicals:
- CH = CH - CH C-ethynyl ethylene- CH3-C C - propynyl
- CH2-C CH - propagil

Isomerism in alkyne.
Alkynes are isomers of functions to:
                                             dinuclear-alkanes (spirit)
                                             -cicloalchine
                                             -diene
Alkynes, n = 4 presents the phenomenon of flavor. position that has given the possibility of triple bond. to occupy different positions in the chain
        Butina shows the next two position isomers
C4H8: CH C-CH 2-CH 3 1 Butina
                CH3-C C-CH 3 2 Butina


Structure alkynesIn chain alkynes meet two types of atmospheres. of C.▪ 2 at. the sp hybridized C - two at. involved in the formation of C tiple connections.▪ at. of sp3 hybridized C - involved in the formation of simple bondAcetylene-first term of homologous series shows a structure (diagonal symmetry) gave hydrocarbon symmetry of 2 at Digene sp. of C. Due sp hybridization angle and distance between the 2 at. R = 1.21 Å triple linked from:
                                                       
-1.54 Å in leg, C-C C ≡ C 1.21 Å
                                                       
-1.33 Å in leg, C = C <180 ˚All due to hybridization and distance decreases from 1.1 in the case of CH-H Csp3 0.6 in Csp-H HC ≡ CH 0.6 ÅConsequently discrete sp hybridization at. of C is the polarization leg. C-H more pronounced than the other leg.Contact CSP - H = leg polar S-on and S + H. Csp Csp-H. This polarization of the bond gives acetylene, respectively alkynes with triple marginal connection weak acid character!
Getting alkynesI ENGINEERING
       
January. Methane: Cracking the arc-
                                 
-The incomplete combustion
        
February. As carbide (CARB) CaC2
II Laboratory methods:         
          1. )  Double elimination hydrohalic of geminal or vicinal dihalo derivatives
          
2. ) Determination Additional alkynes by alkylation of metal acetylenes
I 1. Obtaining methane :       
 At high temperatures 1500 ˚ C => transfer of methane in acetylene ˚
                                                                              
2CH4-> C2H2 +3 H2
       
Industrial transformation is done by two methods differ by the source of energy for reaction
       
It identifies:a process for the cracking of CH4 in the electric arcb incomlete combustion process
a) If this method provided the energy needed for decomposition reaction esste elements and occur between the two metal electrodes fed from a DC source. Besides the main reaction takes place and a number of side reactions and what their stopping place ptr sudden splashing of the reaction medium with cold water. There can still be avoided C reaction forming free
                                                                       
1500 ˚ C
                                       
CH4 -> C +2 H2
               
The method is applied to Borzesti

       
b)   In the case of this process methane is introduced into the reactor utilizt on the one hand, to obtain acetylene RTP, RTP and on the other hand the supply of heat by combustion. And in this case secondary reactions occur most important of which is the reaction for obtaining synthesis gas
                               
CH4 +1 / 2O2-> CO +2 H2
         
Acetylene carbon 2.Obtinerea Ca
       
As the ionic compound carbide = Ca 2 + and C-2 2 - ion C2 is made up of two atmospheres. The Chidrocarborizati sp joined by a triple leg. and that we find a negative charge each HC ≡ CHIn CaC2cele two positive charges of carbide ions were neutralized by Ca 2 +
                     
Industrial CaC2 (carbide) is obtained by reduction to 2500 ˚ C with metallurgical coke Ca oxide obtained by thermal decomposition of limestone
                      
                        
800-1000 ˚ C
         
------------------- CaCO3> CaO + CO2
            
(Limestone)
                        
2500 ˚ C
         
CaO + 3C ----------------> CaC2 + CO
                                                         
(Carbide)

             
CaC2 is an ionic carbide (acetylene) to hydrolyze the metal release in normal conditions with acetylene. Reaction applies to both small-scale genre. Acetylene when oxyacetylene welding and industrial scale.
            
The reaction is violent and fast
        
CaC2 +2 H2O --------------> Ca (OH) 2 + C2H2
                                                                   
(Acetylene)
                                                       
acetylene generator


Metals LaboratoryJanuary. Removal of hydrohalic of dihalo derivativesa vicinal:Transformation occurs in the presence of KOH / alc at a temperature of 100-150 ˚ C. In the first stage (I) derivative obtained hydrohalic elimination occurs. halog. That in the second (II) phase at higher temperature of 150 ˚ C to remove hydrohalic appropriate alkyne transformation.

                             
Alc alc KOH KOH-HC-CH----------------->-C = CH------------>-C ≡ C-
    
XX 100-150 ˚ CX t> 150 ˚ C
                       
- HX-HX

                          
1,2-dichloroethane
                               
Alc alc KOH KOH
                                
CH2-CH2 ------------> CH = CH2 ------------------> HC ≡ CH
                          
100-150 ˚ C Cl Cl Cl t> 150 ˚ C
                                                            
- HCl-HCl

           
Alkenes not deshidrogeneaza the alkyne.
 The transformation of an alkene in alkyne is achieved through a sequence of
  
reactions such as:KOHalc> C = C <+ Br2 ------ >> C-C <------>-C = C <----->-C ≡ C------> CH2 = ------- CH2> CH ≡ CHBr Br


                                           
100 +50 ˚-HBrCH2 = CH2 2 Br ---> CH2-CH2 ------> CH = CH2 -----------> CH ≡ CH
                          
HBr Br Br Br-t> 150 ˚ C

                                                                           
Alc alc KOH KOHCH3-CH = CH + Br2 -----------> CH3-CH-CH2 --------------> CH3-CH = CH2 ------ -----------> CH3-C ≡ CH
                                                          
100-150 ˚ HBr Br Br-Br t> 150 ˚-HBr

              

                            
CH2 = CH 2 C ≡ CH
                                       
                                       
----------->


                         
Styrene Phenyl acetylene                   
                                                 
Br Br
                              
Br2 + CH = CH 2 C ≡ CH CH-CH2
                                                                                  
Alc KOH
                                     
-----------> ----------->
                                                        
-2HBr


               
b) Double dehydrogenation of a secondary germinal dehalogenat
       
The reaction takes place in the presence of KOH solution in stage Alcolica getting monohalides they correspond vinyl and stage IIA to the alkyne
                                                          
x-Hx-HX-C-CH 2 ------------>-C = CH------------>-C ≡ C-
                                                                                      
x KOH KOH alc alc x
Vacin dihalo derivatives are obtained from the reaction of a group in pentahalide crbonil P
                                                                
x
                      
! C = O, PX5 ----------> C
                                                                      
-Pox3 x
                    
carbonyl gr. Carbonyl
        
  Thus the acetic alkyd can get acetylene

                                                                    
Cl Cl alc KOH
          
CH3-CH = O + 5e ----------> CH3-CH3 ----------> CH3-CH ----------> CH2 = CH- ---------> CH ≡ CH
                                                               
POCl3 Cl-Cl-HClphosphorus oxychloride
                       
CH3 CH3 Cl
                    
C = O + 5e ---------> C -------------> CH = CH ---------> CH3-C ≡ CH
                   
POCl3 CH3-CH3 CH3 Cl Cl-HCl


                                                                      
CH3-CH2C = O ---------> CH3-C ≡ C-CH3
                                                                              
CH3


                                                                                                                                                                                          
  
CH3 CH3-CH2-CH2 Cl
             
C = A + --------- 5c> C ---------> CH3-CH = C-CH 3 ---------> CH3-C ≡ C-CH3
           
CH3 CH3 Cl Cl-HCl

February.
Obtaining higher alkynes by alkylation with halogenated conp (seeextensively composition acetylene subsection ionic substitution reactions at CSP) alkynes with triple marginal reaction with Na metal contact at 150 ˚ C by a substitution reaction of H Csp marginal acetylides getting a monoacid. This acetylene can react with a halogenated taking place subst. Na and the formation of a superior alkyne                                     
 150 ˚ C + + + HR-C ≡ CH + Na --------->-C ≡ C ---------->-C ≡ C ---------->-C ≡ CR
                                  
1/2H2-Nax

       
Thus the accetilena can be achieved by any alkyne triple monoalchinarea marginal edge and the alkyne triple dialchinare a boundless
                                   
                                    
100 ˚ C _ + + X-RCH ≡ CH + Na ---------> CH ≡ C Na --------->-CH ≡ CR
                               
-1/2H2 Na-NaX + Imp ptr chain stretches, entered C
                                                        
(200 ˚ C) -1/2H2
                                                            
+ __ +
                           
NAC NAC ≡
                                                               
                               
2 R'-X
                                                                
--------> R'-C ≡ C-R 'Imp-2Nax because they get triple the middle

  
                
CH4 --------> CH ≡ C-CH3

            
1500 ˚ C + Na +-Cl CH3
                     
2CH4 ---------> CH ≡ CH -------------------> --------- CNA ≡ CH> CH ≡ C -CH3
                                          
-150 ˚ C-1/2H2-3H2-NaCl


                                        
CH4 ---------> CH3-C ≡ C-CH3

                                       
                                                    
1500 ˚ C Na + Na +2 Cl CH3-
               
2CH4 ---------> --------- CH ≡ CH> CH ≡ CNA ---------> ≡ NAC NAC ---------- > CH3-C ≡ C-CH
                                          
-3H2 1500 ˚ C-1/2H2 200 ˚ C-H2-H2-2NaCl



                                                  
                                        
CH4 ---------> CH3-CH-C ≡ C-CH-CH3
                                                                                                                 
Acetylene


            
1500 ˚ C + Na + Na2CH4 ---------> --------- CH ≡ CH> CH ≡ CNA ---------> NaCl ≡ CNA ---------> CH3-CH-Cl + + Cl-NAC NAC ≡ CH-CH3
       
3H2 150 ˚ C-CH3 CH3-NaCl
                                                                                          
---------> CH3-CH-C ≡ C-CH-CH3
                                                                  
NaCl CH3-CH3



Physical Properties
        
Acetylene is a colorless gas with pleasant ethereal odor. Acetylene carbide comes from presenting a garlicky odor due to impurity carbide. It is soluble in water volume ratio 1: 1 (one of the few oil-soluble H2O). The property is due to the acetylene CH bond polarity. It is soluble in organic solvents (acetylene).
          
Can not compress under pressure in steel cylinders as an explosion occurs. Are used to prevent its special steel cylinders filled with a porous mass of asbestos or kisellgen which was impregnated with acetone.
On 12 atm 300 l 1l dissolved acetylene acetylene.


                        
CH3-C = C-CH 3 ---------> CH3-C ≡ CH
                             
CH3 CH3



                                                    
[A] CH3-CH3 CH3 CH3 tilt alc KOH-HClCH3-C = C-CH 3 ---------> C = O + O = C ---------> C ---------> CH2 = C-CH3 ---------> CH ≡ C-CH3
                                          
KHnO4 + H2SO4 CH3 CH3 CH3-CH3 + HCl Cl 5e



                                                                                                                                       
HClCH2 = CH-CH2-CH3 + HCl ---> CH3-CH-CH-CH2-CH3 ------> CH3-CH + CH-CH3 + Br2 ---------> CH3- CH-CH-CH3
                                                                                          
Alc KOH Br Br
       
Alc KOH-HBr
    
---------> CH3 CH3 CH3 = C ---------> CH3-C ≡ C-CH3
   
t.150 ˚ C-HBr alc KOH

CH4 ---------> CH3-CH-C ≡ C-CH-CH3
                                               
CH3 CH3



            
T = 1500 ˚ C + Na + Na + _ + __ + 2 Cl-CH-CH3CH4 ---------> --------- CH ≡ CH> CH ≡ C Na ---------> Na Na ------- C ≡ C ---------> CH3-CH-C ≡ C-CH-CH3
                 
-3H2 -1/2H2 200 ˚ C 200 ˚ C -1/2H2 2NaCl CH3-CH3
2,5-dimethyl-5-EXENA






Chemical Properties:
           
Triple bond of the alkyne component having two links п, alkynes unsaturated character will have a more pronounced than they alkenes.

  
The main reactions:
  
I addition of H2, X2, HX, H2O, CH3COOH, CH = CH-CN, HCN
  
II dimerization reaction
  
III cyclic trimerization reaction
  
IV oxidation reaction
  
V substitution at C sp

  
I hydrogenation reaction

            
Can be defined in two stages, the addition product with different degree of saturation according et.
Addition:a) Total - molecular H2 in the presence of finely divided metals (Ni, Pt, Pd) => dividing triple bond in connection simple. As follows:

                                      
Ni Pt Pd-C ≡ C-2 H 2 ---------------->-CH2-CH2-alkyne alkane

                                  
Ni Pt PdCH ≡ CH +2 H2 ----------------> CH3-CH3Acetylene ethane


                                               
Ni Pt Pd-C ≡ CH 2 CH 3 H 2 ----------------> CH3-CH2-CH3
                                                     
Propane



CH ≡ C-CH2-CH3 Ni Pt Pd
    
1-butene, 2 H 2 ----------------> CH3-CH2-CH2-CH3CH3-C-CH3 butane2-butene



b) part - is done in the corresponding alkene resulting homogeneous catalysis. The reaction is stereo specific reaction the catalyst riding. Thus the use of poisoned Pd catalyst salts Pb 2 +, H => cis isomer