In the cisplatin molecule, the atoms H, Cl, N, and Pt are involved in bonds. H is bonded with N, Pt is bonded with B, and Pt is bonded with Cl. The eletronegativity values for these atoms are as follows: hydrogen (H) is 2.2, nitrogen (N) is 3, platinum (Pt) is 2.3, and Chlorine (Cl) in 3.2. The nature of the bonds is described by the arrows (see Figure 2). Arrows are drawn for each bond from the lower electronegativity value to the higher electronegativity value. All of the bonds in a cisplatin molecule are polar covalent (they are covalent but not absolutely covalent) because the difference in electronegativity between the two atoms involved in each bond is greater than zero (absolutely covalent) but less than 1.7 (neutral).
Please note: Because the above image is 3-Dimensional, it was not possible to draw arrows for all of the hydrogen and nitrogen bonds. Every arrow for these bonds would be drawn from the hydrogen atom to the nitrogen atom.
When two cisplatin molecules bond together, two forces of attraction are present. The first force of attraction is london dispersion forces. These forces are present between every two molecules that come in contact with each other. They are caused by the temporary uneven distribution of electrons in a bond and create a temporary, extremely weak dipole (polar molecule). The other force of attraction present in this situation is dipole dipole forces. This force is a result of an electrostatic attraction between the negative end of one molecule and the positive end of another. With two cisplatin molecules, the negative end (with the electron pairs from the chlorine atoms) of one molecule would attract to the positive end (with the 6 hydrogen atoms) of the other molecule. This is an example of dipole dipole forces. The third type of intermolecular forces (hydrogen bonding) would not be present between two cisplatin molecules. Hydrogen bonding is a special case of dipole dipole where hydrogen makes a temporary covalent bond with an adjacent oxygen, nitrogen, or fluorine atom. In the case of two cisplatin molecules, there are no oxygen or fluorine atoms present. While there are two nitrogen atoms in each cisplatin molecule, hydrogen bonding could not occur because each of the nitrogen atoms are completely surrounded by 3 hydrogen and one platinum atom.
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ReplyDeleteThe molecule itself was very accurate and thoroughly done. it even included arrow and the charges of each different corner. It was three dimensional which was nice, and all the bond angles seemed to be correct.
ReplyDeleteThe molecule said you said in your post is indeed polar. you were correct in your reasoning that the molecule does not have an even number of valence electrons on each of its sides, therefore it is polar.
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