Unsymmetrical Ether Definition:
An ether (R-O-R) where the two R groups are not identical.
Unsymmetrical Ether Explained:
Neutral ethers are generally resistant to nucleophiles in substitution reactions because, the leaving group would have to be RO- , which is a very strong base. The first step in any ether cleavage is by a strong acid. Conjugated acid is always a better leaving group. Protonation of the ether allows for loss of ROH as a leaving group, which is a much weaker base than RO- . This is going to bring forth the next step. Cleavage of the C–O bonds.
Though Ethers can form in various ways, but first must go through steps line the example above.