  The capacity of symmetric instance of the multiple unicast index coding
problem with neighboring antidotes (side-information) with number of messages
equal to the number of receivers was given by Maleki, Cadambe and Jafar. In
this paper we consider ten symmetric multiple unicast problems with lesser
antidotes than considered by them and explicitly construct scalar linear codes
for these problems. These codes are shown to achieve the capacity or
equivalently these codes shown to be of optimal length. Also, the constructed
codes enable the receivers use small number of transmissions to decode their
wanted messages which is important to have the probability of message error
reduced in a noisy broadcast channel. Some of the cases considered are shown to
be critical index coding problems and these codes help to identify some of the
subclasses considered by others to be not critical index coding problems.
