$$3$$ - enthyl - $$4$$ - $$4$$ - dimethylheptane

$$1,1$$ - diethyl - $$2,2$$ - dimethylpentane

$$4, 4$$ - dimethyl -$$5,5$$ - diethylpentane

$$5,5$$ - diethyl - $$4,4$$ - dimethylpentane.