An<unk>  group is an alkene hydrocarbon group with the formula H2C=CH-CH2-.  It is made up of a vinyl group, CH2=CH-, attached to a methylene -CH2.  For example<unk>  alcohol has the structure H2C=CH-CH2OH .  Compounds containing the<unk>  group are often referred to as being<unk> ic.<unk> ic carbons are sp3 hybridized, vinylic carbons are sp2 hybridized.
The site of the saturated carbon atom, where the vinyl group attaches (e.g. next to the OH in<unk>  alcohol) is called the<unk> ic position or<unk> ic site.  A group, such as -OH, attached at an<unk> ic site is sometimes described as<unk> ic. Two examples of simple<unk>  compounds are<unk>  chloride and<unk>  alcohol.
Substituted versions of the above, such as the trans-but-2-en-1-yl or crotyl group (CH3CH=CH-CH2-) may be also referred to as<unk> ic groups.<unk> ic methylene groups show special reactivity such as demonstrated in<unk> ic oxidations, ene reactions and the Trost asymmetric<unk> ic<unk> ation.
Allyl
Bromisoval
Alkane
Oxamyl
Arginine
Saline 
Guanine
Sardine