Documente online.
Username / Parola inexistente
  Zona de administrare documente. Fisierele tale  
Am uitat parola x Creaza cont nou
  Home Exploreaza
Upload





















































loading...

ALCHENELE

Chimie

loading...









ALTE DOCUMENTE

Faza nationala a concursului Chimexpert
Petrol
DETERMINAREA CĂLDURII DE REACŢIE
APA - H2O SI ALTE APE
Varianta 2
Poluarea
Zinc, Cadmiu si Mercur
Acid clorhidric:obtinere si proprietati
Purificarea substantelor prin cristalizare-recristalizare
Despre aspartam

Alchenele

 

Def. - hidrocarburi aciclice care:

1)     contin in structura o legatura dubla C-C (σ+π);

2)     au f.m. generala CnH2n

3)     contin atomi de C in 2 stari de hibridizare sp2 si sp3 (exceptie face etena - doar sp2);

4)     datorita prezentei dublei legaturi in structura, alchenele au NE=1;

- seria īncepe de la n=2;

- denumirea se face īnlocuind -an cu -ena;

- denumirea alchenelor cu catena ramificata respecta regulile cunoscute pentru denumirea izoalcanilor, la care se adauga pozitia dublei legaturi;

- se are in vedere ca in cea mai lunga catena continua dubla legatura trebuie sa aiba indicele de pozitie cel mai mic;

 

Izomerie:

a) de pozitie:

         - apare la C4 si se formeaza ca urmare a modificarii pozitiei dublei legaturi in catena;

                   CH2=CH-CH2-CH3                1 butena

                   CH3-CH=CH-CH3                  2 butena

b) de catena:

         - apare tot de la C4 si se formeaza prin ramificarea catenelor alchenelor liniare;

                   CH2=CH-CH2-CH3                1 butena

                   CH2=C-CH3                          

                             |                                    2 metil propena (izobutena)

                            CH3

c) de functiune:

-       cu cicloalcanii - deoarece cele 2 clase de compusi au aceeasi formula moleculara generala (CnH2n) si aceeasi NE=1;

d) geometrica cis-trans:

-       prezinta alchenele la care este respectata conditia de neidentitate a substituentilor legati de atomii de C implicati in dubla legatura;

CH3-CH=CH-CH3

   b       a      a      b

a≠b  - apare simultan la ambii atomi de C dublu legati;

         ! - nu prezinta izomerie geometrica cis-trans structurile de forma:

1)     H2C=C-CH3

     |

    CH3

2)     R-CH=C-R

        |

       R

3)     R-C=C-R

 |    |

R  R

e) optica;



Metode de obtinere:

1)     deshidratarea alcoolilor la 170-200°C in prezenta de H2SO4 sau H3PO4

CH3-CH2-OH    170-200°C;H2SO4          CH2=CH2 + H2O

                                   etanol                                                                      etena

                                                                       R“““       

                                                                        |  

R-CH-OH    <     R-CH-R“   <       R-C-R““

                                            |                            |  

                                           OH                       OH

                                    Creste viteza reactiei de deshidratare

                       OH

                                                               + H2O

                  ciclohexanol                                           ciclohexena

2)     dehidrohalogenarea derivatilor halogenati in solutii alcoolice de baze tari la temperatura:

              CH3-CH-CH3       KOH alcoolic              CH2=CH-CH3  + HCl

                       |

                       Cl                                                               CH3

                           CH3                                                                     CH3              |

                  2                           KOH alcoolic                                         +               + 2HCl

                                Cl

                                                                 80%                                     20%

                                                                       R“““      

                                                                        |  

R-CH2X     <      R-CH-R“   <       R-C-R““

                                            |                            |  

                                           X                          X

                 Creste viteza reactiei de eliminare a HX

- in functie de natura X, reactivitatea R-X variaza:

               R-F      <       R-Cl           <       R-Br           <       R-I

                                                         Creste viteza de reactie la eliminare

-Regula lui Zaitev:

-       la eliminarea unei molecule de HX sau H2O dintr-un derivat halogenat, respectiv alcool, hidrogenul necesar formarii HX sau H2O se ia de la atomul de C cel mai sarac;

         CH3-CH2-CH-CH-CH3                  KOH alcoolic       CH3-CH2-C=CH-CH3 + CH3-CH2-CH-CH=CH2

                            |       |                                                 |                                    |

                          CH3  Cl                                                        CH3                                CH3

                              2 Cl 3 metil pentan                                                                 3 metil 2 pentena                                   3 metil 1 pentena

                         CH3                                                                                    CH3

                          |                                                        |

         CH3-CH-C-CH2-CH3                                    CH2=CH-C-CH2-CH3 + H2O

                        |        |                                                                      |

                      OH  CH3                                                                                   CH3

         OH                                                             Cl

         |                                                                      |

H3C-C-CH3    H2SO4; -H2O          nu are loc;        H3C-C-CH3    KOH; -HCl              nu are loc;

                |                                                                 |       

         CH3                                                                                                   CH3



                   CH2Cl      KOH                      nu are loc;                       Cl         KOH                  nu are loc;

3)     descompunerea termica a alcanilor si cicloalcanilor;

4)     hidrogenarea alchinelor in prezenta de Pd otravit cu saruri de Pb:

              R-C≡CH       +H2    Pd/Pb2+      R-CH=CH2

5)     tratarea derivatilor dihalogenati vicinali cu Na sau Zn:

              CH2-CH2 + Zn                        CH2=CH2 + ZnCl2

                        |        |

              Cl     Cl

                                                                                                                        

                   1,2 diclor etan

Proprietati fizice:

- alchenele pot fi:

-       gazoase: C2-C4;

-       lichide:  C5-C18;

-       solide: peste C18;

- punctele de fierbere si de topire cresc odata cu masa moleculara, dar sunt mai mici decāt la
   alcanii corespunzatori;

- densitatea este mai mica decāt a apei;

- sunt insolubile in apa, dar solubile in solventi organici;

- sunt incolore si fara miros;

Proprietati chimice:

I.                   reactii de aditie la dubla legatura C=C:

a)     a H2

b)    a X2

c)     a HX

d)    a HOH

e)     a HOCl

II.                reactii de polimerizare - poliaditia;

III.               reactii de oxidare:

1)     blānda:

a)     cu KMnO4/HO-;

b)    cu O2 din aer in prezenta de catalizatori;

2)     energica:

a)     cu KMnO4/H+ sau K2Cr2O7/H+

b)    ozonoliza (+O3+H2O);

c)     arderea šCO2+H2O;

IV.            alte reactii la care participa alchenele:

1)     sinteza "oxo";

2)     alchilarea arenelor;

3)     substitutia in pozitie alilica;


I. reactii de aditie la dubla legatura:

a)     a H2:

              R-CH=CH2 + H2                            Ni,Pt,Pd la 200°C si 200 atm      R-CH2-CH3

             alchena                                                                                           alcan cu acelasi nr. de atomi de C in molecula

b)    a Cl2,Br2:

     R-CH=CH2 + X2                                    R-CH-CH2

         alchena                                                |      |    

                                                          X    X

                                                     derivat dihalogenat vicinal saturat

c)     a HX:

     R-CH=CH2 + HX                         R-CH-CH3

        alchena                                                |

                                                              X

                                                         derivat monohalogenat saturat

d)    a HOH:

     R-CH=CH2     HOSO3H         R-CH-CH3                     +HOH R-CH-CH3   + HOSO3H

                                                                                 |                                     |

                                                OSO3H                          OH

                                           sulfat acid de alchil (ester anorganic)     alcool monohidroxilic saturat

                                        R-OSO3H ≠ R-SO3H

e)     a HOCl:

     R-CH=CH2 + HO-Cl+                            R-CH-CH2

        alchena                                              |       |

                                                             OH   Cl

                                                            clorhidrina

Ų     in cazul alchenelor nesimetrice, la aditia acidului hipocloros, gruparea OH se leaga de atomul de C cel mai substituit:

                                                                        OH

                                                                         |

           CH2=C-CH3 + HOCl                    CH2-C-CH3

                     |                                            |       |

                    CH3                                                           Cl                    CH3

                                                                                                 1 clor 2 metil 2 propanol

II. reactii de polimerizare:

Def.- polimerizarea este procesul chimic in care un numar mare de molecule identice ale
            unor compusi nesaturati se leaga intre ele formānd o molecula unica de dimensiuni
           apreciabile, o macromolecula.

         nCH2=CH2                           -[CH2-CH2]n-

         - unde n, numit grad de polimerizare, reprezinta numarul de molecule de etena care
              alcatuiesc lantul macromolecular, el fiind stabilit prin raportul maselor moleculare ale
              celor 2 substante( ex.: Metena=28;Mpolietena≈50000
š n≈1785)

III. reactii de oxidare:

1) blānda: - are loc cu desfacerea legaturii π din legatura dubla si cu conservarea catenei de atomi de C

a)     oxidarea cu agenti oxidanti ionici: KMnO4 in mediu slab bazic sau neutru š dioli, indiferent de structura alchenei oxidate:


CH2=CH2 + [O]      KMnO4/HO־      CH2-CH2

                                                            |        |

                                                           OH   OH

                                                           1,2 etan diol

-       oxigenul necesar acestor oxidari provine din reactiile redox ale KMnO4 in mediu slab bazic sau neutru:

                   2K+1Mn+7O4-2 + H2+1O-2            2K+1O-2H+1 + 2Mn+4O2-2↓ + 3[O]0

                                    Mn+7        +3ē                     Mn+4    2     reducere(agent oxidant)

                            O-2             +2ē                     O0           3     oxidare(agent reducator)

                   Egsubst(redox)=     š EgKMnO4=

b)    oxidarea cu O2 din aer in prezenta de Ag la t°C (ex. 250°C):

                   CH2=CH2 +O2                                          CH2-CH2       H20                        CH2-CH2

                                                               \                /                      |        |

                                                  O                                 OH    OH

      oxid de etena (epoxid;etoxid)

-       oxidul de etena:

+ are f.m. C2H4O si NE=1;

+ este izomer de functiune cu acetaldehida:       CH3-CH=O

+ are structura si proprietati de eter ciclic;

-       reactii la care participa oxidul de etena:

Ų     reactia cu apa š etan diol;

Ų     reactia cu HCl š etilen clorhidrina;

CH2-CH2 + HCl                       CH2-CH2

   \      /                                      |       |

      O                                      OH   Cl

Ų     reactia cu HCN:

CH2-CH2 +HCN                      CH2-CH2

    \     /                                      |       |        

      O                                      OH  CN               etilen cianhidrina                    

Ų     reactia cu NH3:

CH2-CH2 + NH3                                    CH2-CH2

   \     /                                     |        |

     O                                       OH   NH2                      etanol amina

caz particular:

3CH2-CH2 + NH3                        N(CH2-CH2OH)3

                                        \      /                                            trietanol amina




                                   O

Ų     reactia de alchilare a compusilor organici cu H activ in structura (alcooli, fenoli, acizi, amine) cu oxid de etena (reactie de etoxilare) - permite formarea unor noi legaturi O-C sau N-C;


                                           OH                                                          O-CH2-CH2-OH

                                                    + CH2-CH2                                      

                                                         \      /

                                 fenol                       O                            hidroxi-eter

              fenoli

                                           OH                                                           O-(CH2-CH2-O)n-H

                                                    +nCH2-CH2                                     

                                                         \      /

                                   fenol                     O                               hidroxi-polieter

                   R-COOH + CH2-CH2                          R-COO-CH2-CH2-OH

                             acid                  \     /                                     hidroxi-ester

       acizi                              O

                   R-COOH + nCH2-CH2                        R-COO-(CH2-CH2-O)nH

                             acid                        \      /                                  hidroxi-poliester

                                                                           O              

                       

                                         NH2                                                                                                   NH-CH2-CH2-OH

                                            + CH2-CH2

                                                                                 \      /

                        amina                       O                             azot-(beta hidroxi-etil)-anilina                           

        amine

                                 NH2                                                             N-(CH2-CH2-OH)2

                                            + 2 CH2-CH2

                                                     \      /

                                                         O                           azot, azot-di(beta hidroxi-etil)-anilina

2) energica: - are loc cu ruperea dublei legaturi si distrugerea moleculei, conducānd la    
                       obtinerea de acizi carboxilici, cetone, dioxid de carbon si apa (caz particular este
                       ozonoliza
š aldehide si cetone);

                   - are rol pentru precizarea pozitiei dublei legaturi in structura alchenei in functie de
                       compusii organici ce rezulta la formarea acesteia;

a)     oxidarea energica cu agenti oxidanti puternici: KMnO4/H2SO4 sau K2Cr2O7/H2SO4:

                   2KMnO4 + 3H2SO4                         K2SO4 + 2MnSO4 + 3H2O + 5[O]

                   K2Cr2O7 + 4H2SO4                         K2SO4 + Cr2(SO4)3 + 4H2O + 3[O]

-       structurile alchenelor supuse oxidarii pot fi de forma:

Ų     R-CH=CH2  + 5[O]    KMnO4/H+        CO2 + H2O +R-COOH

                                                                                                acid carboxilic

Ų     R-CH=CH-R'  + 4[O]      KMnO4/H+       R-COOH + R'-COOH

                   Daca R=R' š 2 moli de acelasi acid

                   Daca R≠R' š 2 acizi diferiti

Ų     R-C=CH2 + 4[O]    KMnO4/H+        CO2 + H2O + R-C=O                         

           |                                                                    |

         R'                                                                  R

                                                                            cetona

Ų     R-C=CH-R'' + 3[O]   KMnO4/H+        R-C=O + R''-COOH

          |                                                   |          acid carboxilic

         R'                                                 R'

                                                          cetona

Ų     R-C=C-R'' + 2[O]   KMnO4/H+           R-C=O + R''-C=O

          |    |                                               |                |

         R'  R'''                                          R'             R'''

b)    oxidare energica cu O3 - ozonoliza:

-       se formeaza initial produsi intermediari (ozonide) prin a caror hidroliza se obtin produsii finali de reactie: aldehide, cetone, apa oxigenata;

c)     arderea cu O2 din aer š CO2 si H2O indiferent de structura alchenei

                   CH2=CH2 + 3O2                       2CO2 + 2H2O

                   C4H8 +6O2                              4CO2 +4H2O

IV. alte reactii la care participa alchenele:

         1) sinteza "oxo":

                   CH2=CH2 +CO +H2      presiune ridicata    CH3-CH2-CH=O

                                   propanal

-       reactia este o metoda de obtinere a aldehidelor si de lungire de catena, deoarece in urma ei se formeaza o noua legatura C-C;

2) clorurarea alchenelor in pozitie alilica:

                   CH2=CH-CH3 + Cl2           lumina                     CH2=CH-CH2Cl + HCl

                                                                          3 clor 1 propena (clorura de alil)

-       este o reactie de substitutie la C hibridizat sp3 situat in pozitie vecina dublei legaturi; clorura de alil este un derivat halogenat cu reactivitate marita datorita radicalului alil:

                   CH2=CH-CH2Cl + HCl                    CH2-CH2-CH2

                                                                            |                      |

                                                                           Cl          Cl

                                                                              1,3 diclor propan

3) reactia de alchilare a arenelor:                   

                                                                                           CH2-CH3                                     CH=CH2

                                  + CH2=CH2       AlCl3/H2O             

                                                                              etil benzen                         vinil benzen (fenil etena=stiren)


                             CH=CH2                      -(CH-CH2)n-

                                           polimerizare

                             stiren

                                                                polistiren

                                              copolimerizare cu butadiena

                                                                                 cauciuc butadien-stirenic

                                                                                                   CH3

                               + CH2=CH-CH3    AlCl3/H2O                                   CH            -H2                   C=CH2

                                                                                                    CH3                                         |

                                                                                                                                   CH3

                                                                            izopropil benzen (cuman)              α metil stiren (2 fenil propena)

                            C=CH2  polimerizare              CH3

                             |                                     |

                            CH3                            -(C-CH2)n-

                                                                  |              poli α metil stiren

                                                                 C6H5

                                                copolimerizare cu butadiena      cauciuc butadien α metil-stirenic

!OBSERVATII:

1)  alchenele cu dubla legatura ,marginala formeaza prin oxidare energica cu KMnO4/H+ sau cu K2Cr2O7/H+,  CO2 si H2O;

2)    dintre izomerii de structura ai unei f.m., consuma la oxidarea energica cel mai mic volum de oxigen, respectiv de solutie de agent oxidant, structurile cele mai ramificate;

3)    reactia de oxidare energica sau blānda cu agenti oxidanti ionici, sunt reactii de diferentiere intre alchene si cicloalcani: CICLOALCANII nu se oxideaza cu K2MnO4/H+ sau cu K2Cr2O7/H+, respectiv nici cu KMnO4/HO-;

CICLOALCHENE

 

Oxidarea cicloalchenelor:

I. oxidarea blānda - cu KMnO4 in mediu slab bazic sau neutru => dioli ciclici saturati
                                     indiferent de structura cicloalchenei:


                     + [O]     KMnO4/HOÆ               OH      

                                                               OH

                                                  1,2 ciclohexan diol

                                                                       

                     CH3                                                                      OH

                             + [O]     KMnO4/HOÆ                 CH3

     OH

                                                           1 metil 1,2 ciclopentan diol

-       reactiile au loc cu conservarea catenei ciclice de C;

II. oxidarea energica:

a)     cu KMnO4/H+ sau K2Cr2O7/H+ => acizi dicarboxilici, cetoacizi sau dicetone, in functie de structura cicloalchenei oxidate:

          

                     CH

                    /   \\             + 4[O]    KMnO4/H+           HOOC-CH2-COOH

             H2C - CH                                                        acid malonic


              H2C-CH2

                   |      ||             + 4[O]    KMnO4/H+           HOOC-(CH2)2-COOH

              H2C- CH                                                        acid succinic

          

                     CH2

                    /   \

             H2C     CH                   + 4[O]         KMnO4/H+                        HOOC-(CH2)3-COOH

                  |       ||                                                           acid glutaric

      H2C- CH       

                    


CH2

           /   \

             H2C     CH

         |       ||            + 4[O]        KMnO4/H+             HOOC-(CH2)4-COOH

    H2C      CH                                                                 acid adipic

                    \   /

                     CH2

                    

                     CH3

                      |

                     CH2

                    /   \

             H2C     CH                   + 4[O]        KMnO4/H+             HOOC-CH-(CH2)2-COOH

                  |       ||                                                               |

      H2C- CH                                                                   CH3

                                                                                                                                                acid α metil glutaric

            CH3

              |

             C

                    /   \\

             H2C     CH                   + 3[O]       KMnO4/H+             CH3-C-(CH2)3-COOH

                  |       |                                                            ||

      H2C- CH2                                                     O      

                                                                                     acid δ ceto-hexanoic

-       numerotarea catenei acizilor carboxilici īncepe de la gruparea carboxil;

             CH3

              |

             C

                    /   \\

             H2C     C-CH3  + 3[O]       KMnO4/H+             CH3-C-(CH2)3-C-CH3

                  |       |                                                            ||               ||

      H2C- CH2                                                     O             O

             1,2 dimetil ciclopentena                                                    2,6 heptadiona

b)    cu O3 (ozon) => dialdehide, dicetone, cetoaldehide;

c)     arderea => CO2 + H2O;

                    

                    


loading...


Document Info


Accesari: 62363
Apreciat:

Comenteaza documentul:

Nu esti inregistrat
Trebuie sa fii utilizator inregistrat pentru a putea comenta


Creaza cont nou

A fost util?

Daca documentul a fost util si crezi ca merita
sa adaugi un link catre el la tine in site

Copiaza codul
in pagina web a site-ului tau.




Coduri - Postale, caen, cor

Copyright © Contact (SCRIGROUP Int. 2017 )