carrageenan

ι-carrageenan

formula | C_24H_34O_31S_4 Hill formula | C_24H_34O_31S_4-4 name | ι-carrageenan IUPAC name | [(1S, 2R, 3R, 5R, 8S)-8-[[(2S, 3R, 4R, 5R, 6R)-3, 4-dihydroxy-6-(hydroxymethyl)-5-sulfonatooxy-2-tetrahydropyranyl]oxy]-3-[[(2R, 3S, 4R, 5R, 6S)-5-hydroxy-2-(hydroxymethyl)-6-[[(1S, 2R, 3S, 5R, 8S)-3-hydroxy-2-sulfonatooxy-4, 7-dioxabicyclo[3.2.1]octan-8-yl]oxy]-3-sulfonatooxy-4-tetrahydropyranyl]oxy]-4, 7-dioxabicyclo[3.2.1]octan-2-yl] sulfate alternate names | [(1S, 2R, 3R, 5R, 8S)-8-[(2S, 3R, 4R, 5R, 6R)-3, 4-dihydroxy-6-(hydroxymethyl)-5-sulfonatooxy-tetrahydropyran-2-yl]oxy-3-[(2R, 3S, 4R, 5R, 6S)-5-hydroxy-2-(hydroxymethyl)-6-[[(1S, 2R, 3S, 5R, 8S)-3-hydroxy-2-sulfonatooxy-4, 7-dioxabicyclo[3.2.1]octan-8-yl]oxy]-3-sulfonatooxy-tetrahydropyran-4-yl]oxy-4, 7-dioxabicyclo[3.2.1]octan-2-yl] sulfate | gelatin, vegetable | Irish moss mass fractions | C (carbon) 30.4% | H (hydrogen) 3.62% | O (oxygen) 52.4% | S (sulfur) 13.5%

Draw the Lewis structure of ι-carrageenan. Start by drawing the overall structure of the molecule, ignoring potential double and triple bonds: Count the total valence electrons of the carbon (n_C, val = 4), hydrogen (n_H, val = 1), oxygen (n_O, val = 6), and sulfur (n_S, val = 6) atoms, including the net charge: 24 n_C, val + 34 n_H, val + 31 n_O, val + 4 n_S, val - n_charge = 344 Calculate the number of electrons needed to completely fill the valence shells for carbon (n_C, full = 8), hydrogen (n_H, full = 2), oxygen (n_O, full = 8), and sulfur (n_S, full = 8): 24 n_C, full + 34 n_H, full + 31 n_O, full + 4 n_S, full = 540 Subtracting these two numbers shows that 540 - 344 = 196 bonding electrons are needed. Each bond has two electrons, so we expect that the above diagram has all the necessary bonds. However, to minimize formal charge oxygen wants 2 bonds. Identify the atoms that want additional bonds and the number of electrons remaining on each atom. The net charge has been given to the most electronegative atom, oxygen, in 4 places: In order to minimize their formal charge, atoms with large electronegativities can force atoms with smaller electronegativities on period 3 or higher to expand their valence shells. The electronegativities of the atoms are 2.20 (hydrogen), 2.55 (carbon), 2.58 (sulfur), and 3.44 (oxygen). Because the electronegativity of sulfur is smaller than the electronegativity of oxygen, expand the valence shell of sulfur to 6 bonds (the maximum number of bonds it can accomodate) in 4 places. Therefore we add a total of 8 bonds to the diagram, noting the formal charges of the atoms. Double bonding sulfur to the other highlighted oxygen atoms would result in an equivalent molecule: Answer: | |

molar mass | 946.7 g/mol

CAS number | 9062-07-1 PubChem CID number | 11966245 SMILES identifier | C1C2C(C(O1)C(C(O2)O)OS(=O)(=O)[O-])OC3C(C(C(C(O3)CO)OS(=O)(=O)[O-])OC4C(C5C(C(O4)CO5)OC6C(C(C(C(O6)CO)OS(=O)(=O)[O-])O)O)OS(=O)(=O)[O-])O InChI identifier | InChI=1/C24H38O31S4/c25-1-5-12(52-56(31, 32)33)9(27)10(28)22(46-5)49-14-8-4-44-18(14)20(55-59(40, 41)42)24(48-8)51-16-11(29)23(47-6(2-26)15(16)53-57(34, 35)36)50-13-7-3-43-17(13)19(21(30)45-7)54-58(37, 38)39/h5-30H, 1-4H2, (H, 31, 32, 33)(H, 34, 35, 36)(H, 37, 38, 39)(H, 40, 41, 42)/p-4/t5-, 6-, 7-, 8-, 9-, 10-, 11-, 12+, 13+, 14+, 15+, 16-, 17+, 18+, 19-, 20-, 21+, 22+, 23+, 24-/m1/s1/fC24H34O31S4/q-4 MDL number | MFCD00151512