What is the bond order in Connection Table files and how is its value determined?
Double bonds are bit encoded using a bitmask (so 13 = 8 + 4 + 1). The values of the bits are as follows:
- 1 The second line is on the left (looking from the first atom to the second)
- 2 The two lines are centered
- 8 (A modifier to the previous two values, indicating that the user specifically set the positioning. Without this bit, ChemDraw calculated the positioning automatically)
- 4 A double bond with one dashed and one solid line
- 16 A double bond with one bold and one solid line
- 32 A crossed bond.
- 64 A double bond with two dashed lines
The default value, 0, indicates a normal (two solid lines) double bond, with the second line on the right (looking from the first atom to the second).
Using the example above, 13 (= 8 + 4 + 1) means a double bond with one dashed and one solid line (4), where the user specifically wants (8) the second line to be on the left (1).