The present disclosure provides double stranded nucleic acid comprising first and second oligonucleotides wherein the second oligonucleotide is complementary to the first oligonucleotide. At least one of the first and second oligonucleotides comprises a 5′ modified nucleoside or 5′ modified nucleotide having Formula IIb: wherein Bx is a heterocyclic base moiety, T2 is an internucleoside linking group linked to one of the oligonucleotides, and each of q1 to q7 are selected from a list of substituents. In certain embodiments, T2 is a phosphodiester or phosphorothioate linkage and formula IIb is a 5′-nucleotide. In certain embodiments, T2 is a non-phosphate linkage and formula IIb is a 5′-nucleoside. In certain embodiments, the present double stranded nucleic acid provides oligonucleotides that are expected to hybridize to a portion of a target RNA resulting in loss of normal function of the target RNA.