It is widely used as a packaging material and as insulation for electric wires and cables.It is also used for making squeeze bottles, refrigerator tray, pipes, radio and T.V. 00��0�1�1@�r�HҌ@�ľ˛!|F^� hV� Reactions take place in presence of O3/CH2Cl2 , 196-200 K and Zn/H2O. Alkenes are characterized by the presence of a double bond which consists of a strong C-C, σ-bond and a weak C-C π-bond. 3) Ethene is employed for the preparation of ethyl alcohol and ethylene glycol. x�Ľˮ%K�8��8�{䑛�[3I�Р�*eCA�RT������R�����Fr�E����nU&.␛F��n۞|��c�l�c���߾�ӿ�?�ӟ����q,��^?���?�Ƿ/۶ޟg#��b���|��Mr��˿�'Z�������ǟ���;�����~����ɗ�Vlg�\��q����N3�u���q�G�>��8l�v3c����?��?�'\������~���5��������?~�w_�G4��6�h���o�}��������_�v��WCnH~^�r^��k�?�q|���ȷ�}n�ǹ����/��� o�>���8�~����������8���Ur��˵���P��+���ޡi��ɱ��Cs�������?��fƻm��^������ݶm�\�[o��:O{������o�����k���?����s��w�?��?���Y|��㧏���O�������Ƈ?�������g#c�g�ph8���7_���^���7�����n�������o��)4�ރǐ��e�N�m�}��C�0~>�ӷ�{oz�S[3@��v.�w����?�����ߌ���ֿ��DZ�?��`��Xv{H_� 6_a�i�y��ρW ���m|c����N��9��������DG�c�^C��n�9�c�����_G���#%�5~*{j�-�9��o��u���A�`?�zB�5��e�{�w7z�u���:�8��UQ�c�`���� z;����v���S�_����3���4�h}�Y?hHR����u��+G���v6�8�ѧ���I���n��f�N_��x�=%��ۿ� :��s,�=�i8�m�N�A�3`�$`�4�8�����!�{�q/c0��{�N��?wC�F;�Ѭ/&�ͪ1=��H�^{$��c���!�q��P�;���I�Fi�Q|���i �F��9_i"'�4����I����4ɔ`'��;8��YG��Bb�Z� The melting point of cis-1,2-dichloroethene is lower than that of trans-1,2-dichloroethene. During the addition of bromine to alkene, the orange red colour of bromine is discharged since the dibromine formed is colourless.This is a test for unsaturation in organic compounds. Addition of alcohol 6. Such reagents are called, A double bond consists of a σ- bond and a π-bond. Further, due to poor overlapping between the two p-orbitals, a π-bond is always weaker than a a-bond. 3) Polymerization of substituted ethenes: A number of polymers can be obtained by using substituted ethenes as monomers. 3) From vicinal dihalides or 1,2-dihaloalkanes: Dihalogen derivatives of alkanes in which the two halogen atoms are present on adjacent carbon atoms are called vicinal or 1,2-dihaloalkanes . The addition of unsymmetrical reagents such as HX, H, In the presence of peroxides such as benzoyl peroxide , the addition of HBr to unsymmetrical alkenes take place contrary to Markovnikov’s rule way.This is known as, The addition of HBr to alkene in the presence of peroxide occurs by, 4) Addition of elements of hypohalous acid –. If sodium is used instead of zinc, and the reaction is carried out in ether ,only a small amount of propene is formed, the major product being hex-3-ene. The addition of unsymmetrical reagents such as HX, H2O , HOX to unsymmetrical alkenes occurs in such a way that the negative part of the adding molecule goes to that carbon atom of the double bond which carries lesser number of hydrogen atoms. • Learn the IUPAC system for naming alkenes, alkynes, an d aromatic rings. of a trans-isomer is much higher than that of the corresponding cis- isomer. With non- terminal alkenes , ketones or carboxylic acid or both of these product are obtained depending upon the nature of alkene. Alkenes undergo electrophilic reaction.They are of two types: 1) In electrophilic substitution reaction, one σ C-H bond is broken and a new σ-bond between one of the doubly bonded carbon atoms and the electrophile is formed. The π-bond is formed by sideways overlapping of unhybridised p-orbitals of two carbon atoms above and below the plane of Polymerization is a process in which a large number of simple molecule combine to form a big molecule.The simple molecule are called monomers while the big molecules is called a macromolecule or polymer. tert-butyl chloride is the major product. The positive end of this bromine dipole behaves as an electrophile and is attracted by the π-electrons of the ethene molecule to form a π-complex which subsequently gives the carbocations and the bromide ion.This step is slow and hence is the rate determining step of the reaction. Consequently, the m.p. This is due to the reason that the molecules of a cis- isomer being less symmetrical, are weakly held in the crystal lattice than the corresponding more symmetrical trans-isomer. 4) Boiling point : The boiling point of cis isomer are higher than those of the trans isomer. This method is useful for purifying alkenes or for protecting double bond.For this purpose, NaI may be used instead of zinc dust. In cis but-2-ene the dipole moment of two C-CH3 bonds are inclined at an angle of 60° and hence have a resultant equal to 0.33 D. In case of trans-but-2-ene the two dipole moment being equal and opposite cancel out each other and therefore dipole moment of trans-but-2-ene is zero. 156 0 obj <>stream Chlorine and bromine in the presence of water readily add to alkene to from halohydrins. Your email address will not be published. A mixture of ethanol and conc H2SO4 in the ratio of 1:2 by volume is added from a dropping funnel into a round bottom flask containing anhydrous Al2(SO4)3 and sand in whichAl2(SO4)3 catalyzes the reaction whereas sand is used to avoid frothing during the process. Ethene produced by the above method contains impurities of SO. CH2=CH2 + 4 [O] ——> 2HCOOH ——-> 2CO2 +2 H2O, CH3CH=CH2 + 4 [O] ——-> CH3COOH + [HCOOH] —–>CO2 + H2O. CH3-CH=CH-CH3 + HCl ——–> CH3-CHCl-CH2-CH3. %PDF-1.5 %���� 3) Dipole moment : cis-isomer of an alkene is found to be more polar than the trans isomer. 3 CH3CH=CHCH3 + 2KMnO4 + 4H2O ——-> CH3-CHOH-CHOH-CH3 + 2 MnO2 + 2KOH. – The simplest of the functional groups are the hydrocarbons, which include the alkanes, alkenes, alkynes, and aromatic hydrocarbons. Alkenes are compounds that consist of carbons and hydrogens bonded together with a carbon-carbon double bond. Therefore, these molecules are unsymmetrical and hence do not pack well in the crystal lattice. very common in nature; they have distinctive chemical properties, often absorb visible light, and as a result are often colored compounds. 1) If the proton adds on the terminal carbon atom of the double bond, a 2° carbocation is formed. Overall two-step conversion of an alkene first into alkyl hydrogen sulphate followed by hydrolysis with boiling water to form alcohols is called indirect hydration of alcohols. h�bbd```b``�`�q?�d_"Yb��^��V0i %�쏢 1) Polymerization of ethene : When ethene is heated to 473 K under a pressure of 1500 atm and in presence of a trace of oxygen , it undergoes polymerization to from polythene. Physical Properties of Alkenes. Physical Properties. Therefore, alkenes are readily attacked by reagents or compounds which are in search of electrons. Such reagents are called electrophiles or electrophilic reagents. As a result, lesser amount of energy is required to break the crystal lattice of the cis-isomer and consequently the solubility of the cis-isomer is higher as compared to that of the trans-isomer in the same solvent. • Alkenes have low melting points and boiling points. %%EOF 1) Lower members of the family are used as fuels and illuminates. Bromine molecule itself is non-polar but when it comes close to an ethene molecule, the π-electrons of double bond begin to repel the electron pair holding the two bromine atoms together in the bromine molecule.As a result, bromine molecule gets polarized. The π-electrons form an electron cloud which lies above and below the plane of σ-bonded carbon atoms.
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