TUM Quantum Chemistry Laboratory
Prof. N. Rösch

Exercise 1

Click here to load into WebLab Topic: Z-matrix of Formaldehyde

You will start the Quantum Chemistry Laboratory by constructing a Z-matrix of formaldehyde H2CO. The formaldehyde molecule exhibits C2v symmetry, i.e. the structure is planar. Experimental values [1] for the bond distances and the angle H-C-O are

bond distances, Å C-O 1.208
C-H 1.116
bond angle, degree H-C-O 121.8

Use these experimental values and describe the structure of the formaldehyde molecule by a Z-matrix. Fill out the form given below.

For the moment, do not care about "special options"; they are subject of the next exercise. The solution of the exercise is a Z-matrix of formaldehyde in a form that can be read by the program Gaussian. Having filled out the form, you can automatically generate this program input by pressing the button "Generate Program Input".

If you discover a mistake, correct the input, or reset the form altogether by pressing the "Reset" button at the bottom of the page.

Visualize your solution with the help of the WebLab Viewer. (If you have not done so already, it is high time to install the WebLab Viewer.)

If you want to see a correct solution, press the button labeled "Solution" at bottom of this page. Note that several correct solutions exist for the Z-matrix.


Atom Distance to atom Angle Dihedral angle
N1 symbol N2 N1-N2 special
N3 N1-N2-N3 special
N4 N1-N2-N3-N4 special
no. no. Å no. degree no. degree

Z-Matrix as Program Input

(WebLab Viewer must be installed) Erase form content


[1] K. Takagi and T. Oka, "Millimeter wave spectrum of formaldehyde", J. Phys. Soc. Japan, 18 (1963) 1174.

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