Chemistry Question!

College Life
1

<p>I have a question!
Why in formaldehyde (CH2O) hydrogens are attached to Carbon atom and not oxygen? </p>

<p>Please help!!
Thanks!</p>

2

<p>Draw out the chemical structure of formaldehyde. Oxygen has a double bond to carbon. Oxygen also only has 2 valence electrons. Therefore, oxygen is not capable of forming more than two bonds (yes, ozone, but that’s a little different) and cannot bond to hydrogen.</p>

<p>Also telling is that the molecule is an aldehyde, which tells you that there is a carbonyl. A carbonyl oxygen will have nothing else bonded to it but the carbon.</p>

3

<p>Hydrogen can be attached to oxygen. It is an example of tautomerism. However, the structure with hydrogen attached to oxygen will be much less stable. To understand that, draw the structure of the tautomeric form. It is possible in two ways:
H–C–O–H and H–C(-)=O(+)–H
In the first structure, the carbon atom has an incomplete octet. In the second, carbon and oxygen both have a complete octet, but nevertheless this structure contains distributed charges and therefore is energetically less favorable compared to the common formaldehyde molecule H2C=O. That is the reason why formaldehyde naturally exists in the form where both hydrogens are attached to carbon atom. However, the particles like H–C–O–H can exist for a short time under specific conditions, such as the electron impact in mass-spectrometer’s ionizer cell.</p>