| 11. | The numbered carbons in the open-chain forms correspond to the same numbered carbons in the hemiacetal forms.
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| 12. | Similarly, in excess alcohol, the aldehyde, its hemiacetal, and its acetal all exist in solution.
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| 13. | In crystal form, three conformers occur as hemiacetal dimers with a 1, 4-dioxane ring skeleton:
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| 14. | Hemiacetal results from addition of the alcohol's hydroxyl group to the carbon in the C = O bond.
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| 15. | The cyclic hemiacetal forms of aldoses can open to reveal an aldehyde and certain ketoses can undergo tautomerization to become aldoses.
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| 16. | D-ribose in itself is a hemiacetal and in equilibrium with the pyranose "'3 " '.
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| 17. | The resulting molecule has an hemiacetal or hemiketal group, depending on whether the linear form was an aldose or a ketose.
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| 18. | Though the cyclic forms of sugars are usually heavily favoured, hemiacetals in aqueous solution are in equilibrium with their open-chain forms.
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| 19. | In this mechanism, the terminal olefin undergoes hydroxymercuration to produce the first intermediate, compound "'2 "', a hemiacetal.
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| 20. | The formation of the hemiacetal causes carbon number 1, which is symmetric in the open-chain form, to become asymmetric in the cyclic version.
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