Page numbers refer to Organic Chemistry third edition by Paula Yurkanis Bruice

 

This is a five-step synthesis of 3-octene:

 

Step 1.  Methyne is reacted with NaNH2 and 1-bromopropane to form 1-pentyne.

Step 2.  This is then reacted with NaNH2 and 1-bromopropane to form 4-octyne.

Step 3.  4-octyne is then converted to 4-octene using Na, NH3 (liq).

Step 4.  HBr is added to form 4-bromooctane.

Step 5.  The Br is then eliminated when CH3O- in CH3OH, forming 3-octene. Here only half of the desired product is formed since during the elimination reaction both 3-octene and 4-octene are formed.