**2. SO based diols**

The most excessively used SO based diol in PU production is fatty amide diol or fatty alkan‐ diol‐amide [FAD] (Figure 2). FAD is obtained by the base catalysed amidation of SO with diethanolamine. The structure of FAD is determined by the fatty acid composition of the starting SO.

**Figure 2.** Figure 2. FAD from (a) Linseed (35.0‐60.0 % Linolenic acid), (b) Soybean (43.0‐56.0 % Linoleic acid) and (c) Karanj (44.5–71.3 % oleic acid), Nahor (55‐66% oleic acid) , Jatropha (37‐63 % oleic), Olive (65‐80 % oleic acid)

The reaction proceeds by nucleophilic acyl substitution bimolecular (SN2) reaction mechanism. As the name suggests, FAD contains an amide group, with two hydroxyl ethyl groups directly attached to amide nitrogen along with the pendant aliphatic chain of SO. FAD is derived from different SO such as Linseed (*Linum ussitassimum*), Soybean (*Glycine max*), Karanj (*Pongamia glabra*), Nahor (*Mesua ferrea*), Jatropha (*Jatropha Curcus*), Olive (*Olea europea*), Coconut (*Cocos nucifera*) and others [20‐30] (Figure 2). FAD is used as raw material for various polymers such as PU, poly (esteramide) and poly (ether amide).
