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CH2Cl2 has the greatest dipole moment. CCl4 is the only one without a dipole. The electronegativity difference in the two atoms causes a polar bond which results in a partial charge on each atom. These molecules are in a tetrahedral configuration, so the two Cl atoms in CH2CL2 do not cancel out, they are additive. These charges act like vectors when in a magnetic field. Think of the geometry or build a model of the molecule and you will see why CHCl3 results in a lower net dipole than CHCl2
CH3Cl has maximum dipole (1.87 D) in case of polyatomic molecules(4 atoms one). is how 2 are additive and 3 isnt? all three are at 109.5 degrees from each other one component should add up isnt it?? and CCl4 will be 0 dipole agreed.. resultant of 2 dipoles: Ures=Sqrt(u^2+u^2+u x u x cos (109.5)) =sqrt(u^2(2+cos(109.5)))= u sqrt(2-2*0.325) = u (1.16) which is greater than u ie dipole of one.. so it is additive in case of 2 and even additive in case of three Ures=u(1.694) (warning: maths work could be wrong) then, how can this (what is mentioned in question) happen..
CH3Cl has greater dipole moment than CH2Cl2 because of symmetry of molecule: |dw:1338548074133:dw| |dw:1338548105497:dw|
in CH2Cl2 both Chlorine atoms are at apporx. 109 degrees then according to vector addition law .. using cosine rule resultant vector of dipole should be ..GREATER than what would have been by a single chlorine atom.. then why is CH3Cl has more dipole? this vector summation theory doesnt support it. any alternate reasons? or is there any fault in my maths?
i found something interesting: http://dwb.unl.edu/Teacher/NSF/C06/C06Links/www.uis.edu/7Etrammell/organic/introduction/polarity.htm
Thanks, Shameer, for your contribution, but please give the link when you copy someone else's work. http://answers.yahoo.com/question/index?qid=20090403064807AA9J3Cc
hehehe here is also something for reading: http://www.vidyasagar.ac.in/journal/maths/Vol12/JPS12-14.pdf