The positive and negative charges attract. Branched alkanes have a lower boiling point than their corresponding unbranched isomer. Branching produces less efficient packing and thus weakens the intermolecular interactions. Since C-H groups are not hydrogen bond donors, alkanes disrupt the hydrogen bonding network of water. Like dissolves like.
Alkanes are very soluble in other organic solvents.
The longest continuous carbon is the parent compound. Number the carbons in the parent chain so that substituents have the smallest possible numbers. Find each alkyl substituent and assign it a number according to which carbon it is attached. Prefixes are not used to determine alphabetical order. Use commas between numbers and dashes between numbers and words.