Topic: Alcohols – structure

Target group

Elementary school student (grades 7. and 8.)

Core curriculum

Primary school. Chemistry.

IX. Hydrocarbon derivatives. Pupil:

1) writes summary formulas, draws semi‑structural (group) and structural formulas of straight‑chain monohydroxy alcohols containing up to five carbon atoms in a molecule; creates their systematic names; divides the alcohols into mono- and polyhydric acids.

General aim of education

The student writes formulas of alcohols and creates their names

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• to divide alcohol depending on the number of functional groups;

• to define the concept of alcohol;

• the general formula of monohydric alcohols;

• to indicate a functional group in the formula of the organic compound;

• to recognize alcohols based on the functional group;

• to call on the basis of the sum formula of alcohol;

• to write summary and structural formulas of alcohols.

Methods/techniques

• activating

  • discussion.

• expository

  • talk.

• exposing

  • film.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• interactive whiteboard, tablets/computers.

Lesson plan overview

Introduction

1. The teacher hands out Methodology Guide or green, yellow and red sheets of paper to the students to be used during the work based on a traffic light technique. He presents the aims of the lesson in the student's language on a multimedia presentation and discusses the criteria of success (aims of the lesson and success criteria can be send to students via e‑mail or posted on Facebook, so that students will be able to manage their portfolio).

2. The teacher together with the students determines the topic – based on the previously presented lesson aims – and then writes it on the interactive whiteboard/blackboard. Students write the topic in the notebook.

3. Health and safety – before starting the experiments, students familiarise themselves with the safety data sheets of the substances that will be used during the lesson. The teacher points out the need to be careful when working with them.

Realization

1. The teacher introduces students to the issue of alcohol. He writes on the board the division of alcohols into monohydroxy and polyhydroxy - the students copy the data to the notebooks.

2. The teacher writes on the board the general formula of monohydric alcohols and gives a definition of these compounds. Students write information in notebooks.

3. The teacher displays on the board the presentation „Rules for creating alcohol formulas”.

4. The lecturer gives the formula on the array of homologous monohydric alcohols. He discusses - on the example of methanol - the principles of using this formula to create total monohydric alcohol formulas.

5. The instructor divides the students into groups. He gives them ball models. He recommends that, based on a series of homologous alcohols, they build models of the first five alcohols.

6. The teacher asks students to do interactive exercises in the abstract.

Summary

1. The student indicated by the teacher sums up the lesson, telling what he has learned and what skills he/she has been practicing.

Homework

1. Listen to the abstract recording at home. Pay attention to pronunciation, accent and intonation. Learn to pronounce the words learned during the lesson.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Alcohols – structure

Alcohols are derivatives of hydrocarbon where carbon atom (or atoms) was (were) replaced with hydroxyl functional group $\text{–OH}$, so‑called hydroxyl group (hydrogenium is the Latin name of hydrogen, oksygenium – of oxygen).
If one hydrogen atom in an alkane molecule is replaced with one hydroxyl group, then a compound consisting of a hydrocarbon chain ($\text{R}$) and alcohol functional group $\text{–OH}$ is formed.

Formula of monohydric alcohol is:

$\text{R – OH}$

Alcohol names can consist of one or two parts.

Alcohols containing one hydroxyl group in the molecule, like hydrocarbons, form a homologous series. The name of an alcohol derived from an alkane is formed from the name of an alkane with the same number of carbon atoms in the molecule, adding to it the ending -ol and removing the ending -e, e.g. methanol is a methane derivative, ethanol – an ethane derivative. Names of alcohols consisting of two parts are formed by adding the name derived from particular hydrocarbon to the ‘alcohol’, changing the ending -ane into -yl, e.g. methyl alcohol.

${\text{C}}_{\text{n}}{\text{H}}_{\text{2n+2}}$

General formula of monohydric alcohol is formed by replacing one hydrogen atom by hydroxyl functional group $\text{–OH}$ in alkanes.

${\text{C}}_{\text{n}}{\text{H}}_{\text{2n+1}}\text{OH}$

The table contains alcohols ranked according to the increasing number of carbon atoms. Each of the following compounds differs from the previous one by group $\text{–}{\text{CH}}_{\text{2}}\text{–}$. This series is called the homologous series.

In monohydric alcohol molecules the hydroxyl group can be attached to various atoms of carbon. This phenomenon is called position isomerism. The number contained in the alcohol name indicates the number of the carbon atom where the $\text{–OH}$ group is located.

Alcohol with the simplest structure derives from methane, which means that its molecule contains only one carbon atom. One hydrogen atom in methane is replaced by functional group. Due to the number of $–\text{OH}$ groups, it is a monohydric alcohol. Methanol is a methane derivative.

The process of alcohol fermentation occurs under the influence of a special yeast species found in the peels of ripe grapes (or other fruits). Glucose – sugar contained in fruit juice – under favourable conditions, undergoes a chemical reaction where ethyl alcohol is produced.

Reaction equation – in words:

$\text{glucose}\stackrel{\text{yeast}}{\to }\text{ethyl alcohol + carbon dioxide}$

Reaction equation – molecular form:

${\text{C}}_{\text{6}}{\text{H}}_{\text{12}}{\text{O}}_{\text{6}}\stackrel{\text{yeasts}}{\to }{\text{2CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{OH +}{\text{2CO}}_{\text{2}}$

The reaction equation shows that alcohol fermentation is a process that takes place under the influence of yeast. Its products are ethyl alcohol and carbon dioxide.

Ethyl alcohol contains as many carbon and hydrogen atoms as ethane. Due to this similarity of composition, ethanol is one of ethane derivatives.

Based on the position of carbon in the periodic table, we can conclude that the atom of this element has four valence electrons. Thus, it can create up to four bonds in organic compounds. In the ethyl alcohol molecule, the carbon atoms are connected with each other by a single bond. The oxygen atom forms two bonds: one with a hydrogen atom and one with a carbon atom. Each of the hydrogen atoms is monovalent, i.e. it creates only one bond.

Molecular formula of alcohol does not inform how the molecule is build. Thus, to determine differences in structure of various of alcohols, structural forms are used.

Ethanol formula:

${\text{C}}_{\text{2}}{\text{H}}_{\text{5}}\text{OH}$

• The alcohol fermentation products are ethanol and carbon dioxide.

• Monohydric alcohols are compounds in which one hydrogen atom has been replaced by a monovalent group $–\text{OH}$.

• Methanol and ethanol contain one functional group in their molecules. These are monohydric alcohols.

• Alcohols have many applications.