"Alkanes:" C_nH_(2n+2);
"Alkene:" C_nH_(2n);
"Alkyne:" C_nH_(2n-2);
"Alkyl residue:" C_nH_(2n+1);
"Aldehyde/ketone:" C_nH_(2n)O;
"Cycloalkane:" C_nH_(2n)
A fully saturated hydrocarbon, an alkane, has general formula C_nH_(2n+2): n =1, methane; n =2, ethane; n =3, propane. BY reason of their formula alkanes are said to "HAVE NO DEGREES of UNSATURATION."
Where the formula is C_nH_(2n) or C_nH_(2n)O_m, each 2 hydrogens LESS than 2n+2 represents a "degree of unsaturation". Each degree of unsaturation represents a double bond OR a ring. Compare cyclopropane to propane or hexane to cyclohexane to cyclohexene; does this formulation hold?
Where there is nitrogen in the formula we substract NH from the given formula before assessing its degree of saturation. For "methylamine", H_3CH_2CNH_2, we assess a formula of C_2H_6, no degrees of saturation. For pyridine, C_5H_5N, we assess C_5H_4, 4^@ of unsaturation, i.e. 3 olefinic bonds, and one ring..........
