Chem U4 AOS 2

Interpolate

Infer values from a graph within the range of data

Miscibility

Ability of two or more substances to dissolve in each other

Mobile phase

Fluid in a chromatography system that carries the sample over the stationary phase

Origin

Line at which samples are placed in paper and thin-layer chromatography

Paper chromatography

Chromatography technique using absorbent paper

Peak area

The area enclosed between the peak and the baseline on a chromatogram

Retention time ($Rt$ )

Time taken for a component in a sample to pass through an HPLC column

Resolution (chromatography)

Degree of separation between two different peaks on a chromatogram

Stationary phase

Solid onto which the components of a sample adsorb

Thin-layer chromatography

Chromatography technique using a thin stationary phase supported by an inert backing

Hydrogen nucleus

The nucleus of the hydrogen atom, which has an odd mass, allowing it to be detected by an NMR spectrometer.

Integration curve

Curve on a $^1H\text{-NMR}$ spectrum showing the relative number of protons in a proton environment.

Low resolution

Shows only singular peaks without splitting patterns.

$n+1$ rule

The number of splits in a peak is equal to the number of protons in neighbouring proton environment(s) ($n$) + 1.

Non-equivalent proton environments

One or more protons (hydrogen nuclei) attached to different atoms that are in different chemical environments, causing splitting to adjacent protons.

Splitting pattern

The number of peaks shown in a set of peaks corresponding to a single non-equivalent proton environment.

$^{13}C\text{-NMR}$ spectroscopy

Analytical technique that uses electromagnetic radiation and magnetic fields to provide information about the number of non-equivalent carbon environments in an organic compound.

$^{13}C\text{-NMR}$ spectrum

Spectrum of chemical shift values in $\text{ppm}$ relative to a chemical standard (usually TMS).

Carbon-13 nucleus

The nucleus of the carbon-13 isotope, which has an odd mass, allowing it to be detected by an NMR spectrometer.

Chemical shift

The resonant frequency of an atomic nucleus relative to a standard in a magnetic field.

Equivalent carbon environments

One or more carbon-13 nuclei attached to the same atom that are in identical chemical environments and are able to combine with adjacent carbon-13 nuclei to show as one peak in a spectrum.

Non-equivalent carbon environments

One or more carbon-13 nuclei attached to different atoms that are in different chemical environments.

Symmetrical

Made up of exactly identical parts facing each other or around an axis.

Adsorption

Adhering of a component onto the stationary phase

Calibration curve

A graphical representation of the relationship between the concentration of a substance and its corresponding response on a detector

Chromatogram

Visual output of chromatography

Desorption

Release of a component from the stationary phase by dissolving

Eluent

Solvent fluid that moves through a chromatography system

High performance liquid chromatography (HPLC)

Chromatography technique in which the mobile phase and sample are pumped through a tightly packed stationary phase under pressure

Base peak

The most intense peak in a mass spectrum, which is assigned a relative abundance of $100\%$.

Fragment ion

Simple positively charged fragment formed from the cleavage of bonds in the molecular ion.

Fragmentation

The process in which molecular ions undergo bond cleavage to form smaller fragments.

Mass/charge ratio (m/z)

The ratio of the mass of an ion relative to its charge.

Mass spectrometry

Analytical technique used to measure the mass-to-charge ratio of ions in a sample.

Molecular ion

The ion formed when a neutral molecule is bombarded with high-energy electrons.

Molecular (parent) ion peak

The peak in the mass spectrum that corresponds to the molecular ion, which has the highest m/z ratio.

Relative abundance

The abundance/intensity of an ion relative to the base peak.

Absorbance

Measure of the amount of light that is absorbed by a substance.

Fingerprint region

Complex absorption pattern in the region between $400\,cm$ and $1500\,cm$ that is unique to each organic compound.

Infrared light

Invisible electromagnetic radiation that transmits energy.

Infrared spectroscopy

Qualitative analytical technique that uses infrared radiation to analyse bond vibrations, providing information about molecular structures and functional groups.

Infrared spectrum

Graph representing the absorbance of infrared light at different wavelengths within the infrared region of the electromagnetic spectrum.

Transmittance

Measure of the amount of light that passes through a substance.

Wave number

The reciprocal of the wavelength of light measured in $cm$.

'H-NMR (proton NMR) spectroscopy

Analytical technique that uses electromagnetic radiation and magnetic fields to provide information about the number of non-equivalent proton environments in an organic compound and the number of protons in those environments.

'H-NMR spectrum

Spectrum of chemical shift values in ppm relative to a chemical standard (usually TMS).

Equivalent proton environments

One or more protons (hydrogen nuclei) attached to the same atom that are in identical environments and combine with adjacent protons to show as one set of peaks in a spectrum.

High resolution

Shows both singular peaks and distinct sets of peaks with splitting patterns.

Tests to identify C=C

Bromine Water Test

• Decolouration indicates the presence of a carbon-carbon double bond (alkene), addition reaction

Potassium permanganate

• Reaction between KMnO₄ and an unsaturated hydrocarbon, resulting in a colour change.

Tests to identify hydroxyl group

Acidified potassium dichromate/oxidation test

• Primary and secondary alcohols reduce to Cr⁶⁺ to Cr³⁺ ions, colour change from orang to green, shows a postive with aldehydes and not ketone

Lucas Test

• conc HCl + zinc Chloride, results in an immediate phase separation for tertiary alcohols, forms oily layer after 3-5 mins with secondary alcohol and with primary alcohol reamin colourless unless its heated

Silver mirror test

• Ag(NH₃)₂ and aldehyde creates a silver mirror confirming the precense of a primary alcohol

Esterfication reaction

• Carboxylic acid and a concentrated sulfuric acid catalyst are added to a tube and heated, if fruity smell is smelt, then the test susbtance is an alcohol

Test for carboxyl group

pH test

• Carboxylic acids are weak acids and they partially ionise in solution, resulting in a pH less than 7.

Metal carbonates

• If carboxylic acid reacts with a metal carbonate, it produces carbon dioxide, water, and a salt. Its is confirmed to be CO₂ it turns limewater cloudy

How is purity determined by melting point

The more pure the substance the smaller the range of the melting point

How does rinsing water left in the burette affect the substance under analysis

Underestimated in burette and Overestimated in the titration flask, since the burette solution is diluted with water, so more is used to reach the equivalence pointwhich leads to an inaccurate calculation of concentration.

How does rinsing water left in the pippette affect the substance under analysis

Overestimated in burette and Underestimated in the titration flask, since the solution aliquot in the titration flask is diluted

Why does the indicator changing colour too soon afect the substance under analysis

Overestimated in burette and Underestimated in the titration flask

How does water in titration flask affect the titration

No effect