[a confused chiral girl]

Hi!~

I am stuck on trying to determine the major product of this diagram below. I know that the reagent Li reacting with the aldehyde will form a secondary alcohol, but I don't know how these structures look like. I don't know which one to pick, these are the choices : 3,6-dimethyl-4-heptanol, 2,3-dimethyl-3-heptanol, 2,5-dimethyl-4-heptanol.

thank you!

[Custos]

Think about the reaction this way and draw it out. The lithium regent is essentially a carbon framework with an anion. The anion attacks the electropositive carbon of the aldehyde to give you (after quenching) the alcohol product. You can easily put the carbon chain together from this and the name is then simple.

[a confused chiral girl]

thanks for teaching me Custos 
I am a bit confused about where the H on the end of the original structure went, because I thought when you attack the electrophile, the whole structure of the nucleophile would be attached and the H would still be on the end...

[Custos]

The H is still there. I ommited it for clarity but that obviously made it less clear. Does this help? The same H is carried through in green.

[a confused chiral girl]

Oh yes 

I didn't see that...now it is crystal clear!!
thank you Custos for going through all the trouble to draw out the steps explicitly. now I understand how the structure can be added on...thank you thank you!