What is the geometry of dichloromethane?

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In summary: The other two have =CIPr and IPrIPr.In summary, the conversation discusses the geometry of dichloromethane and the change in bond angles and lengths after optimization. It also delves into the concept of molecular energies and stability in isomers, specifically (E)-1,2-diisopropylethene, (Z)-diisopropylethene, and 1,1-diisopropylethene. The influence of bulky groups and electron density is mentioned, along with the concept of hyperconjugation. The participants also discuss the reasons for the change in bond angles and lengths, with steric strain and the size of the groups being considered. Ultimately, the conversation highlights the
  • #1
jnimagine
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organic chem!

What is the geometry of dichloromethane?? Before optimization, Cl-C-Cl bond is 109.5, H-C-Cl bond is 67.8... so it must be tetrahedral... but after optimization, do the angles get bigger?? why?
and also, the bond length increases...
Why do angles and the bond length in dichloromethane increase when it's geometrically optimized??

Another question is...
when we examine (E)-1,2-diisopropylethene, (Z)-diisopropylethene, and 1,1-diisopropylethene... the molecular energies are different. (E) isomer has the least energy, so it's more stable and the 1,1-isomer's the least stable... i think...? why? does it have to do with how the bulky groups are far apart or not??
The most confusing part! is how the bond angle for these isomers are in a weird order... E has the smaller angle, and Z has the biggest... I can't figure out why! > . <
 
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  • #2


Are you accounting for the influence of electronegativity and electron density?

Do you know about the concept of hyperconjugation?

What bond angles are you referring to specifically?
 
  • #3


jnimagine said:
What is the geometry of dichloromethane?? Before optimization, Cl-C-Cl bond is 109.5, H-C-Cl bond is 67.8... so it must be tetrahedral... but after optimization, do the angles get bigger?? why?
and also, the bond length increases...
Why do angles and the bond length in dichloromethane increase when it's geometrically optimized??
Bond angles change (from an ideal tetrahedron) for what reason? What bond length did you start from? The bond length for C-H?

Another question is...
when we examine (E)-1,2-diisopropylethene, (Z)-diisopropylethene, and 1,1-diisopropylethene... the molecular energies are different. (E) isomer has the least energy, so it's more stable and the 1,1-isomer's the least stable... i think...? why? does it have to do with how the bulky groups are far apart or not??
Yep.
The most confusing part! is how the bond angle for these isomers are in a weird order... E has the smaller angle, and Z has the biggest... I can't figure out why! > . <
What angle are you measuring? The angle between the double bond and the IPr group or between the vinyl carbon's hydrogen and it's IPr group?
 
  • #4


chemisttree said:
Bond angles change (from an ideal tetrahedron) for what reason? What bond length did you start from? The bond length for C-H?


Yep.

What angle are you measuring? The angle between the double bond and the IPr group or between the vinyl carbon's hydrogen and it's IPr group?

1. Does the bond angle change to reduce steric strain maybe?? and we measured the C-Cl bond length which was about 1.76 whereas after optimization, it went up to about 1.79A.
So again, does making the bonds be farther apart make it more stable??

2. ok the bond angle of C=C-C was measured for the three isomers..
so in increasing order it was E<1,1-ipr<Z... this doesn't quite make sense for me...
 
  • #5


jnimagine said:
1. Does the bond angle change to reduce steric strain maybe?? and we measured the C-Cl bond length which was about 1.76 whereas after optimization, it went up to about 1.79A.
So again, does making the bonds be farther apart make it more stable??
Bigger groups like Cl don't like to be as close together as smaller groups like H.

2. ok the bond angle of C=C-C was measured for the three isomers..
so in increasing order it was E<1,1-ipr<Z... this doesn't quite make sense for me...
You can think of the IPr group as a big bulky thing that is pushing against its neighbor groups. It pushes against the geminal hydrogen and the other vinylic groups on the other carbon. You have to come to grips with the fact that hydrogen is small relative to IPr and that the vinyl (=CH2) carbon is smaller than IPr but bigger than hydrogen.
 
  • #6


chemisttree said:
Bigger groups like Cl don't like to be as close together as smaller groups like H.


You can think of the IPr group as a big bulky thing that is pushing against its neighbor groups. It pushes against the geminal hydrogen and the other vinylic groups on the other carbon. You have to come to grips with the fact that hydrogen is small relative to IPr and that the vinyl (=CH2) carbon is smaller than IPr but bigger than hydrogen.

hmm I'm confused... aren't the IPr groups for all three isomers pushing against =CH2 regardless of how they're arranged?
 
  • #7


jnimagine said:
hmm I'm confused... aren't the IPr groups for all three isomers pushing against =CH2 regardless of how they're arranged?

You have =CH2 in only one of the isomers.
 

FAQ: What is the geometry of dichloromethane?

1. What is the molecular formula for dichloromethane?

The molecular formula for dichloromethane is CH2Cl2, which means it contains one carbon atom, two hydrogen atoms, and two chlorine atoms.

2. What is the molecular geometry of dichloromethane?

The molecular geometry of dichloromethane is tetrahedral. This means that the molecule has a central carbon atom bonded to four other atoms, with a bond angle of approximately 109.5 degrees.

3. Can you describe the shape of a dichloromethane molecule?

The shape of a dichloromethane molecule is best described as a "bent" or "V-shaped" structure. This is due to the two chlorine atoms being bonded to the central carbon atom on opposite sides, causing a slight bend in the molecule.

4. What is the polarity of dichloromethane?

Dichloromethane is a polar molecule. This is due to the difference in electronegativity between the carbon and chlorine atoms causing an unequal distribution of electrons, resulting in a partial negative charge on the chlorine atoms and a partial positive charge on the carbon atom.

5. How does the geometry of dichloromethane affect its physical properties?

The geometry of dichloromethane affects its physical properties in several ways. The tetrahedral shape allows for a relatively high boiling point and melting point, while the partial charges on the molecule contribute to its polarity and ability to dissolve in polar solvents. The bent shape also results in a dipole moment, which contributes to the molecule's overall polarity and reactivity.

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