A Toy Model of Chemical Reaction Networks - TBI - Universität Wien

4.2. GRAPH REWRITE ENGINE 41
O
O
O
H
Half−Rule 1
C
C
Ψ
O
H
O
O
Half−Rule 2
C
C
C
C
Ψ
Join−Rule
Ψ
Ψ
C
Ψ
Ψ
C
Left Graph
Context
Right Graph
O
+
O
O
OH
Figure 4.3: Aldol Reaction. Top: rewrite rule; the two half-rules describe
the local changes in the reacting molecules during Aldol condensation, while
the half-rule-join describes only intermolecular changes; notice the special
label Ψ, acting as anchor for the intermolecular bond to be formed. Only the
elements in black are actually contained in the rules, the other elements are
displayed to hint at their embeddings. Bottom: Application to the synthesis
of β-hydroxy-carbonyls.