Chemistry terms: D

D

Daniell cellalso Daniell cells

A voltaic cell made of a zinc electrode in zinc sulfate solution and a copper electrode in copper(II) sulfate solution, joined by a salt bridge; zinc is the anode.

Introduced in R3.2 Electron transfer reactions

Data bookletalso chemistry data booklet, the booklet

The IB booklet of equations, constants, the periodic table and data tables (bond enthalpies, enthalpies of formation and combustion, electrode potentials, spectroscopic data and more) that every candidate has in every paper.

Database investigationalso database investigations, secondary data investigation

An investigation whose data are selected from an existing data set rather than measured by the student; its method describes how the data were chosen, filtered and sampled.

Degree of unsaturationalso degrees of unsaturation

The number of multiple bonds and rings in a molecule; each mole of ${{\mathrm{H}{\vphantom{X}}_{\smash[t]{2}}}}$ added in hydrogenation removes one degree of unsaturation.

Introduced in R3.2 Electron transfer reactions

delocalizationHL only · also delocalisation, delocalised, delocalized

The spreading of electrons over three or more atoms, so that they are not confined to one bond or one atom; delocalized pi electrons form where p orbitals on adjacent atoms overlap sideways.

Introduced in S2.2 The covalent model

delocalization energyHL only · also resonance energy, stabilization energy, delocalisation energy

The extra stability of a species with delocalized electrons compared with one localized structure; for benzene about $152\ \text{kJ mol}^{-1}$, from enthalpies of hydrogenation.

Introduced in S2.2 The covalent model

Delocalized electronalso delocalised electrons, sea of electrons, electron sea

An electron that is not attached to one atom or bond but is shared by many atoms and free to move through a structure, as in metals, graphite and benzene.

Introduced in S2.3 The metallic model

Dependent variablealso dependent variables

The variable that is measured in an experiment, which changes in response to the independent variable.

Introduced in R2.2 How fast? The rate of chemical change

depositionalso desublimation

The change of state directly from gas to solid, which releases energy (exothermic), for example ${{\mathrm{I}{\vphantom{X}}_{\smash[t]{2}}\mskip2mu (\mathrm{g})\xrightarrow{}\mathrm{I}{\vphantom{X}}_{\smash[t]{2}}\mskip2mu (\mathrm{s})}}$

deshieldingHL only · also deshielded

In NMR, the decrease in shielding of a hydrogen atom when nearby electronegative atoms or π electrons draw electron density away from it, moving its signal to higher chemical shift.

Introduced in S3.2 Functional groups: classification of organic compounds

deuterated solventHL only · also CDCl3, deuterated solvents

A solvent such as ${{\mathrm{CDCl}{\vphantom{X}}_{\smash[t]{3}}}}$ in which hydrogen atoms are replaced by deuterium, used for $^{1}\text{H}$

deuteriumalso hydrogen-2, heavy hydrogen, D

The isotope of hydrogen with one proton and one neutron in its nucleus, ${{{\vphantom{X}}^{\hphantom{2}}_{\hphantom{1}}{\vphantom{X}}^{\smash[t]{\vphantom{2}}\mathllap{2}}_{\vphantom{2}\mathllap{\smash[t]{1}}}\mathrm{H}}}$

diamond

An allotrope of carbon in which each atom is covalently bonded to four others tetrahedrally in a three-dimensional network; very hard and does not conduct electricity.

Introduced in S2.2 The covalent model

diffusionalso diffuse, diffuses

The net movement of particles from a region of higher concentration to one of lower concentration, caused by their random motion.

Introduced in S1.1 Introduction to the particulate nature of matter

Dilutionalso diluting

Adding solvent to a solution. The amount of solute stays the same, so $C_1V_1 = C_2V_2$

DipeptideHL only · also dipeptides

The molecule formed when two amino acids join by a condensation reaction, linked by a peptide (amide) link, with the release of water.

Introduced in S2.4 From models to materials

dipole momentalso net dipole, net dipole moment

A measure of the separation of positive and negative charge in a molecule; a molecule whose bond dipoles do not cancel has a net dipole moment.

Introduced in S2.2 The covalent model

dipole-induced dipole forcealso dipole-induced dipole forces

An attraction between the permanent dipole of a polar molecule and the dipole it induces in a neighbouring non-polar particle.

Introduced in S2.2 The covalent model

dipole–dipole forcealso dipole-dipole forces, dipole–dipole forces

An attraction between the permanent dipoles of neighbouring polar molecules.

Introduced in S2.2 The covalent model

Directly proportionalalso direct proportionality, proportional

Two quantities are directly proportional when doubling one doubles the other; a graph of one against the other is a straight line through the origin.

Introduced in S1.5 Ideal gases

Discrete variablealso discrete variables

A variable that can take only certain separate values, such as the number of carbon atoms in a molecule.

Displacement reactionalso displacement reactions, halogen displacement

A reaction in which a more reactive element takes the place of a less reactive one in a compound, for example ${{\mathrm{Cl}{\vphantom{X}}_{\smash[t]{2}}\mskip2mu (\mathrm{aq}) {}+{} 2\,\mathrm{Br}{\vphantom{X}}^{-}\mskip2mu (\mathrm{aq})\xrightarrow{}2\,\mathrm{Cl}{\vphantom{X}}^{-}\mskip2mu (\mathrm{aq}) {}+{} \mathrm{Br}{\vphantom{X}}_{\smash[t]{2}}\mskip2mu (\mathrm{aq})}}$

Disproportionationalso disproportionates, disproportionation reaction

A redox reaction in which atoms of the same element in one species are both oxidized and reduced, as in ${{\mathrm{Cl}{\vphantom{X}}_{\smash[t]{2}} {}+{} 2\,\mathrm{NaOH}\xrightarrow{}\mathrm{NaCl} {}+{} \mathrm{NaClO} {}+{} \mathrm{H}{\vphantom{X}}_{\smash[t]{2}}\mathrm{O}}}$

distillationalso simple distillation, distil, distilled, distillate

Separation of a liquid from a mixture by boiling it and condensing the vapour in a separate container; used for a solvent from dissolved solids or liquids with very different boiling points.

Introduced in S1.1 Introduction to the particulate nature of matter

Distractoralso distractors

A wrong option in a multiple-choice question, written so that a particular mistake in reasoning or calculation leads to it.

double bondalso double bonds

A covalent bond made of two shared pairs of electrons; shorter and stronger than a single bond between the same atoms.

Introduced in S2.2 The covalent model

doubletHL only · also doublets

An NMR signal split into two lines of equal height (1 : 1) by one hydrogen atom on an adjacent carbon atom.

Introduced in S3.2 Functional groups: classification of organic compounds

Ductilealso ductility

Able to be drawn out into a wire without breaking, a typical property of metals.

Introduced in S2.3 The metallic model

dynamic equilibriumalso equilibrium, chemical equilibrium, state of equilibrium

The state of a reversible reaction in a closed system in which the forward and backward reactions continue at equal rates, so the concentrations of all species remain constant.

Introduced in R2.3 How far? The extent of chemical change