Alcohols and Their Reactions
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Questions and Answers

What type of reaction is the conversion of an alcohol to an alkene?

  • Dehydration (correct)
  • Halogenation
  • Reduction
  • Oxidation

Tertiary alcohols are easily oxidized using acidified potassium dichromate(VI).

False (B)

What color change is observed when an alcohol is oxidized with potassium dichromate(VI)?

orange to green

Primary alcohols can be oxidized to aldehydes, and further oxidized to ______.

<p>carboxylic acids</p> Signup and view all the answers

Match the following alcohols with their oxidation products:

<p>Primary Alcohol = Aldehyde (then Carboxylic Acid) Secondary Alcohol = Ketone Tertiary Alcohol = No Reaction</p> Signup and view all the answers

Which reagent can be used to convert an alcohol to an iodoalkane?

<p>Red phosphorus and iodine (B)</p> Signup and view all the answers

Haloalkanes contain nonpolar bonds due to the similar electronegativity of carbon and halogen atoms.

<p>False (B)</p> Signup and view all the answers

What type of product is formed when a secondary alcohol is oxidized?

<p>ketone</p> Signup and view all the answers

What is the primary function of the condenser in a reflux apparatus?

<p>To cool and condense vapours, returning them to the flask (C)</p> Signup and view all the answers

In a distillation setup, the liquid with the higher boiling point evaporates first.

<p>False (B)</p> Signup and view all the answers

What property difference allows a separating funnel to separate liquids?

<p>density</p> Signup and view all the answers

The purer a substance, the ______ to the databook boiling point it will be.

<p>closer</p> Signup and view all the answers

Match each piece of apparatus with its primary use:

<p>Reflux Apparatus = Heating a reaction mixture while preventing loss of volatile substances Distillation Apparatus = Separating liquids with different boiling points Separating Funnel = Separating liquids with different densities Thiele Tube = Measuring boiling point</p> Signup and view all the answers

What is the purpose of using an inverted capillary tube when determining a substances boiling point?

<p>To allow the condensed liquid to be drawn into (B)</p> Signup and view all the answers

Redistillation is done to obtain a less pure product.

<p>False (B)</p> Signup and view all the answers

When determining boiling point, what observation is made to determine the exact boiling point temperature?

<p>condensation</p> Signup and view all the answers

The fingerprint region of an IR spectrum is unique to each molecule and can be used to identify it.

<p>True (A)</p> Signup and view all the answers

The absorption of infrared radiation by atmospheric gases containing C=O, O–H, and C–H bonds, such as CO₂, H₂O, and CH₄, is linked to ______.

<p>global warming</p> Signup and view all the answers

Which of the following is NOT a use of Infrared Spectroscopy?

<p>Identifying different molecules (C)</p> Signup and view all the answers

Match the following steps in TOF mass spectrometry with their corresponding descriptions.

<p>Ionization = Positively charged ions are accelerated towards a negatively charged detection plate. Acceleration = A sample is vaporized and injected into the mass spectrometer where a high voltage is passed over the chamber. Ion Drift = The ions are deflected by a magnetic field into a curved path. Detection = When positive ions hit the negatively charged detection plate, they gain an electron, producing a flow of charge. Analysis = The current values are used in combination with the flight times to produce a spectra print-out with the relative abundance of each isotope displayed.</p> Signup and view all the answers

What is a nucleophile described as?

<p>An electron pair donor (A)</p> Signup and view all the answers

Nucleophilic substitution can occur for tertiary haloalkanes.

<p>False (B)</p> Signup and view all the answers

What is the purpose of the magnetic field in TOF mass spectrometry?

<p>The magnetic field deflects the ions into a curved path, allowing for separation based on their charge and mass.</p> Signup and view all the answers

What does the 'm/z' value in mass spectrometry represent?

<p>Mass to charge ratio (B)</p> Signup and view all the answers

What type of product is formed when haloalkanes react with aqueous potassium hydroxide?

<p>alcohols</p> Signup and view all the answers

The greater the Mr of the halogen in the polar bond, the ______ the bond enthalpy.

<p>lower</p> Signup and view all the answers

The molecular ion peak in a mass spectrum is the peak furthest to the left, representing the ion with the lowest mass-to-charge ratio.

<p>False (B)</p> Signup and view all the answers

Match the nucleophiles with their products after reaction with haloalkanes:

<p>:NH3 = Amines :OH- = Alcohols CN- = Nitriles</p> Signup and view all the answers

Explain how the relative abundance of each isotope is determined in TOF mass spectrometry.

<p>The relative abundance of each isotope is determined by measuring the current produced when the ions hit the detection plate. A greater current indicates a higher abundance of that specific isotope.</p> Signup and view all the answers

What role do chlorine radicals play in the breakdown of ozone?

<p>They act as catalysts and are regenerated. (B)</p> Signup and view all the answers

CFCs are haloalkanes containing carbon, chlorine, and fluorine atoms, but not oxygen.

<p>True (A)</p> Signup and view all the answers

What is the overall equation for the breakdown of ozone by chlorine radicals?

<p>2O₃ → 3O₂</p> Signup and view all the answers

Which of the following is a common anhydrous salt used for drying compounds?

<p>Magnesium sulphate (A)</p> Signup and view all the answers

Addition reactions are less sustainable than substitution reactions.

<p>False (B)</p> Signup and view all the answers

What is the process called that involves converting an organic compound into a product through multiple stages?

<p>Multi-stage synthesis</p> Signup and view all the answers

Bromine water is used to test for __________.

<p>unsaturation</p> Signup and view all the answers

Match the following tests with the substances they detect:

<p>Bromine water = Unsaturation Acidified potassium dichromate = 1°/2° alcohols Tollens’ reagent = Aldehydes Aqueous silver nitrate with ethanol = Haloalkanes</p> Signup and view all the answers

When analyzing synthetic routes, why is it preferable to choose reagents with fewer safety concerns?

<p>They minimize health risks. (B)</p> Signup and view all the answers

The identification of functional groups can be performed using various tests.

<p>True (A)</p> Signup and view all the answers

What effect does infrared (IR) radiation have on covalent bonds?

<p>It causes them to vibrate and absorb energy.</p> Signup and view all the answers

Which functional group is identified by a sharp peak in the range of 1620-1680 cm-1?

<p>C=C Unsaturated Group (D)</p> Signup and view all the answers

A broad, smooth peak in the IR spectrum indicates the presence of a carboxylic acid functional group.

<p>False (B)</p> Signup and view all the answers

What does the IR spectrum primarily measure when analyzing organic compounds?

<p>Absorbance of infrared radiation by functional groups</p> Signup and view all the answers

The characteristic peak range for the C=O carbonyl group is ________ cm-1.

<p>1680-1750</p> Signup and view all the answers

Match the functional groups with their characteristic peak ranges:

<p>-OH Alcohol Group = 2300-3550 cm-1 C=C Unsaturated Group = 1620-1680 cm-1 C=O Carbonyl Group = 1680-1750 cm-1 -OH Acid Group = 2500-3300 cm-1</p> Signup and view all the answers

Which functional group can be identified by both a C=O bond peak and a broad O–H bond peak?

<p>Carboxylic Acid (C)</p> Signup and view all the answers

At approximately what cm⁻¹ will most organic compounds produce a peak due to C–H bonds?

<p>3000</p> Signup and view all the answers

Infrared spectroscopy can distinguish between aldehydes and ketones solely by their C=O absorption peaks.

<p>False (B)</p> Signup and view all the answers

Flashcards

Alcohol Halide Substitution

The reaction in which a hydrogen halide (such as HBr) reacts with an alcohol, replacing the hydroxyl group (-OH) with a halogen atom (-Br).

Iodoalkane Formation

A method to produce iodoalkanes from alcohol using red phosphorus and iodine. This involves the formation of phosphorus(III) iodide first, followed by the reaction with the alcohol.

Dehydration of Alcohols

A reaction that removes a water molecule (H2O) from an alcohol molecule, resulting in an alkene.

Potassium Dichromate(VI)

An oxidizing agent used in the oxidation of primary and secondary alcohols.

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Oxidation of Primary Alcohols

The process of converting a primary alcohol into an aldehyde and then further to a carboxylic acid using acidified potassium dichromate(VI).

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Oxidation of Secondary Alcohols

The conversion of secondary alcohols into ketones using acidified potassium dichromate(VI).

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Haloalkane Properties

A type of organic compound characterized by a polar bond between a carbon atom and a halogen atom (F, Cl, Br, or I).

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Polar Bond in Haloalkanes

The unequal sharing of electron density in a carbon-halogen bond, making the carbon atom slightly positive (∂+) and the halogen atom slightly negative (∂-).

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Nucleophile

A species that donates an electron pair. They are attracted to positively charged regions of molecules.

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Nucleophilic Substitution

A reaction mechanism where a nucleophile attacks a haloalkane, replacing the halogen. This often results in alcohols, amines, or nitriles.

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Chlorofluorocarbons (CFCs)

A substance containing carbon, chlorine, and fluorine. These are examples of haloalkanes - compounds with a halogen attached to an alkane.

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Ozone Depletion by CFCs

The process where UV radiation breaks down CFCs, producing chlorine radicals that catalyze ozone destruction.

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Free Radical

A highly reactive species with an unpaired electron. They are often responsible for chain reactions, like the breakdown of ozone.

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Haloalkane

A molecule containing a halogen atom bonded to an alkane (saturated hydrocarbon).

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Bond Enthalpy

The strength of a bond, measured by the energy required to break it. Weaker bonds break more easily, leading to faster reaction rates.

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Rate of Reaction

The rate at which a chemical reaction proceeds. Faster reactions occur more quickly.

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Anhydrous Salt

A chemical compound that absorbs water, often used to dry other substances by removing moisture.

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Synthetic Route

A series of chemical reactions that produce a specific product from a starting material.

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Multi-Stage Synthesis

A multi-step process that uses intermediates to generate a final product. Each step involves a chemical reaction.

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Analytical Techniques

Techniques used to determine the structure and identity of organic compounds.

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Functional Group Identification

The process of using specific tests to identify different functional groups present in an organic molecule.

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Infrared Spectroscopy

A type of spectroscopy that utilizes infrared radiation to study the vibrational modes of molecules, providing information about the functional groups present.

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Functional Group

The specific arrangement of atoms and bonds within a molecule that defines its chemical properties.

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Addition Reaction

A chemical reaction in which molecules combine to form a larger molecule, without any atoms being lost.

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Reflux

A technique used in organic chemistry to heat a reaction mixture at a constant temperature without losing any volatile reactants or products.

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Distillation

A method of separating liquids with different boiling points by vaporizing, condensing, and collecting the components.

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Separating Funnel

A technique used to separate two immiscible liquids of different densities by allowing them to form distinct layers.

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Redistillation

The repetition of distillation to further purify a substance by removing remaining impurities.

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Boiling Point

The temperature at which a liquid changes into a gas, used to assess the purity of a substance.

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Thiele Tube

A glass tube with a sidearm used to determine the boiling point of a small sample of liquid.

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Inverted Capillary Tube

A small glass tube placed inside a Thiele tube to measure the boiling point of a substance. The liquid is drawn up into the tube and the temperature at which this occurs is recorded.

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Boiling Point Range

The range of temperature over which a substance changes its state, indicating its purity. A pure substance has a narrow boiling point range while an impure substance has a wider range.

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Fingerprint Region

The region of an IR spectrum from 500-1500 cm⁻¹ that is unique for each molecule, acting like a 'fingerprint' for identification.

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Global Warming and Infrared Absorption

The absorption of infrared radiation by atmospheric gases like CO₂, H₂O, and CH₄, which contributes to global warming.

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Mass Spectrometry

An analytical technique used to identify molecules and determine their relative molecular masses.

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Time of Flight (TOF) Mass Spectrometry

A type of mass spectrometry that measures the time it takes for ions to travel to a detector.

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Ionization

The process of removing electrons from atoms, creating positively charged ions.

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Ion Acceleration

The movement of ions towards a negatively charged detection plate.

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Ion Drift

The bending of ions in a magnetic field, where the radius of the path depends on the ion's charge and mass.

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Detection

The measurement of the current produced when ions hit a detection plate, which reveals the abundance of each ion.

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Characteristic Peaks

The regions of the infrared spectrum where specific functional groups absorb radiation, allowing for their identification.

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Alcohol (-OH) Peak

A broad, curved peak in the IR spectrum, typically found in the range of 2500-3300 cm-1.

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Acid (-OH) Peak

A broad peak in the IR spectrum, typically found in the range of 2500-3300 cm-1, overlapped with the C-H region.

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Unsaturated (C=C) Peak

A sharp peak in the IR spectrum, typically found in the range of 1620-1680 cm-1.

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Carbonyl (C=O) Peak

A sharp peak in the IR spectrum, typically found in the range of 1680-1750 cm-1.

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Interpreting IR Spectra

The process of using the characteristic peaks in an IR spectrum to determine the functional groups present in an organic compound.

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Carboxylic Acid

A compound containing a carbonyl group (C=O) and an alcohol group (-OH) attached to the same carbon atom.

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Study Notes

Alcohols

  • Alcohols contain an -OH group and follow the general formula CnH2n+1OH.
  • They can be classified as primary (1°), secondary (2°), or tertiary (3°) depending on the position of the hydroxyl group.
  • Alcohols are polar molecules due to the large electronegativity difference between carbon and oxygen, allowing hydrogen bonding with water.
  • This hydrogen bonding makes alcohols water-soluble.
  • Alcohols have both hydrogen bonding and van der Waals forces, making them less volatile than alkanes.
  • Alcohols combust in air, reacting with oxygen to form carbon dioxide and water, releasing energy.
  • (Example: 2CH3OH + 3O2 → 2CO2 + 4H2O)

Reactions of Alcohols

  • Combustion: Alcohols react with oxygen to form carbon dioxide and water, releasing energy, making them good fuels.
  • Reaction with halogenating agents: Alcohols can react with halogenating agents (like PCl3) to form haloalkanes, replacing the -OH group with a halogen. This reaction can be used as a test for alcohols.
  • Elimination Reactions: Alkenes can be produced from alcohols through dehydration, where a molecule of water is removed, typically by heating the alcohol with concentrated phosphoric acid.
  • Oxidation of Alcohols:
    • Primary alcohols can be oxidised to aldehydes and further to carboxylic acids with acidified potassium dichromate(VI).
    • Secondary alcohols are oxidised to ketones with acidified potassium dichromate(VI).
    • Tertiary alcohols are not easily oxidised.

Haloalkanes

  • Haloalkanes contain polar bonds because halogens are more electronegative than carbon.
  • This creates a partial positive charge on the carbon and a partial negative charge on the halogen.
  • They are classified as primary, secondary, or tertiary based on the position of the halogen in the carbon chain.
  • Reactivity varies between halogens, decreasing down the group from fluorine to iodine. This is due to decreasing bond enthalpy.

Substitution Reactions of Haloalkanes

  • Haloalkanes react with aqueous alkali (like NaOH) in a nucleophilic substitution reaction to form alcohols.
  • Haloalkanes react with ethanolic potassium hydroxide (KOH) to form alkenes via an elimination reaction.
  • Haloalkanes react with aqueous silver nitrate to form precipitates, with the colour of the precipitate indicating the halide ion. The rate of precipitate formation correlates to the stability of the haloalkane. Iodoalkanes are hydrolysed faster than bromoalkanes, which are faster than chloroalkanes.

Nucleophilic Substitution Mechanism

  • Nucleophiles, electron-pair donors, attack haloalkanes in a specific mechanism.
  • This depends on the type of nucleophile and the structure of the haloalkane (primarily 1° and 2°).

Environmental Concerns

  • Organohalogen compounds, like CFCs, can break down the ozone layer in the atmosphere through a catalytic reaction.
  • Ultraviolet radiation initiates the breakdown.

Organic Synthesis

  • Practical Skills: Heating under reflux (for reactions that need extended heating) and distillation (to separate liquids with different boiling points) are important techniques.
  • Synthetic Routes: In the preparation of an organic compound, choosing appropriate synthetic routes based on reagents, byproducts, and reaction conditions to ensure efficiency and safety is important.
  • Multi-stage Synthesis: In the preparation of complex organic molecules, steps involving intermediate molecules can improve efficiency.

Analytical Techniques

  • Infrared Spectroscopy (IR): IR radiation causes covalent bonds to vibrate, and the absorbed energy is used to identify functional groups by their unique absorption patterns in the IR spectrum.

  • Mass Spectrometry: This is used to identify molecules and determines the mass of the organic molecule. It shows the breakdown of the original molecule and identifies the fragments.

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OCR A Chemistry A-level Alcohols, Haloalkanes & Analysis Detailed Notes PDF

Description

This quiz covers the chemical properties of alcohols, including their structure, classifications, and reactions such as combustion and reaction with halogenating agents. It is designed to test your understanding of alcohol chemistry and their significance in organic reactions.

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